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MathWorks could be the leading developer of mathematical computing software for engineers and scientists.
MATLAB math programming application written by MathWorks. Quoting off their web page : MATLAB is often a high-level language and interactive environment for numerical computation, visualization, and programming.
MATLAB is really a complete environment for high-level programming, together with interactive data analysis. MATLAB excels at numerical computations, specially when dealing with vectors or matrices of internet data. Symbolic math is obtainable through an add-on toolbox which utilizes a MuPAD kernel.
There a variety of add-on toolboxes that extend MATLAB to specific aspects of functionality, like statistics, finance, signal processing, image processing, bioinformatics, etc. You can find an index of toolboxes that is generated by MathWorks. There is also a list /products/connectionsof some add-on products produced and sold by other programs, and many users place their own functions or collections of functions for the MATLAB Central File Exchange.
Questions in regards to the name MATLAB often arise. MATLAB represents MATrix LABoratory. See this breakdown of MATLAB.
This wiki contains strategies to questions commonly answered within the newsgroup sometimes abbreviated cssm, which is usually a forum for discussing the business of the usage of MATLAB. It occasionally includes questions relevant to similar software applications like Octave. Any topic in connection with MATLAB is acceptable. Additionally, you will see occasional discussions regarding related math topics in the more abstract form.
Before posting, please skim through this document to find out if your question was already answered. If it is has not yet, there could possibly be information here that will help you better be aware of the issue and phrase your question.
This Wiki FAQ was entered November 2010 in the Google cache in the old original Mathworks FAQ.
GNU Octave is often a freely available software program with a language mostly works with MATLAB : /software/octave/.
Scilab can be a scientific program for numerical computations in the user-friendly environment. It is fully open source and contains a parallel version. /.
IDL Interactive Data Language is usually a commercial computer software with applications just like MATLAB. It is very like minded to image processing and 3D visualization. IDL was formerly that is generated by Research Systems Inc., now a part of IIT Visual Information Solutions
Igor Pro is often a commercial graphing, data analysis, image processing and programming software program that combines extensive programmability and numerical analysis tools with powerful visualization tools.
O-Matrix is often a commercial MATLAB - like program. In fact it possesses a great MATLAB compatibility mode, that this authors claim can execute native MATLAB code 5-10 times faster than MATLAB. Readers who may have used this package ought to send me a better explanation.
LyME runs an acceptable subset of MATLAB code about the Palm platform. Available for free at Thanks to Martin Cohen because of this info.
Fredrik Hekland suggests: Back inside the days when I used OS/2, Euler became a good option to MATLAB no less than for the simple operations I needed in those days. I see that Euler is living, now as GNU GPLed OSS. /MGF/homes/grothman/euler/
Stefan Mueller is involved with developing a MATLAB - like program called JMathLib, designed in Java. See /.
SciPy and NumPy are open source Python packages for scientific computations.
FreeMat looks very much like MATLAB, yet it's open source. It runs under Linux, Mac OS X and Windows plus the newest version 4.0 premiered 2009-10-09. /
A cell is really a flexible form of variable that will hold any kind of variable. A cell array is actually an assortment of those cells. Its somewhat confusing so lets make an analogy. A cell is like a bucket. You can throw something you like into the bucket: a string, an integer, a double, an assortment, a structure, even another cell array. Now let's imagine you have numerous buckets - numerous cells or even a Cell Array. Each bucket can contain different things, or they could all offer the same kind of variable. Bucket 1 could possess a string, while bucket 2 could contain an image variety of uint8s, while bucket 3 is usually a int32. Or all buckets could contain strings of varied lengths. Its totally flexible.
ca1 myString; ca2 myInteger; ca3 myDoubleArray; ca4 rgbImage; ca5 myStructure;
The braces must be read as valuables in, for those times you say ca4 rgbImage, that you are saying that this article of cell 4 would be the variable rgbImage.
Another solution to use the cell should be to refer for the cell itself, in lieu of the belongings in it, as well as that you make use of parentheses. The item it means must be a cell. For example ca1 is often a cell, ca2 can be a cell, and ca3 can be a cell, although those cells contain variables of arbitrary, and maybe different, types. To make something a cell, you enclose it in braces, similar to this:
ca1 myString; ca2 myInteger; ca3 myDoubleArray; ca4 rgbImage; ca5 myStructure;
This pair of code is entirely comparable to the first number of code. For the very first line, its basically like saying Lets have a bucket a cell and place the string involved with it - thats what myString on its own is. Then lets take that bucket to make it bucket 1, replacing any bucket that had been already there. In other words, go ahead and take cell myString and produce it be element 1 bucket 1 on the cell array called ca. It uses parentheses this means it is the term for the whole single bucket the bucket together with contents whilst the first pair of code used braces which is the term for only the contents on the bucket. So ca1 equals the cell myString, while ca1 equals the string myString for the reason that braces said to acquire the contents in the cell. In other words, ca1 says dont provide me the bucket while using string inside, just provide me the string alone, minus the bucket. Its merely a slight difference - a somewhat different method of considering it. Saying
are equivalent to the most part. You can use in any event and I dont really think the best way or the other is absolutely preferred. You may use whatever approach is easier for you to take into consideration it. Maybe the best way will be more intuitive to suit your needs than the other way, yet, these are equivalent.
Cell arrays are much like structures, that you just probably will be more familiar with, in this both are containers which could hold variables of an variety of various sorts arrays, strings, scalars, even other structures or cells. The difference is always that with structures you consider the different members or fields by their name , while with cells you talk about them by their index number ca1.
Here is a few demo code that can help explain cell arrays, along with the type of classes you will get when you have braces or parentheses:
Initialize a cell array with three various sorts of contents. % First cell contains an int32, second cell includes a string, % as well as the third cell posesses a double array. ca int32123, abcdef, piones3 % Lets see whats in cell 1 plus the difference between % using and making use of. ca1cell ca1 fprintfnThe class of ca1cell is %sn, classca1cell ca1contents ca1 fprintfThe class of ca1contents is %snn, classca1contents % Lets see whats in cell 2 and also the difference between % using and taking advantage of. ca2cell ca2 fprintfThe class of ca2cell is %sn, classca2cell ca2contents ca2 fprintfThe class of ca2contents is %snn, classca2contents % Lets see whats in cell 3 as well as the difference between % using and utilizing. ca3cell ca3 fprintfnThe class of ca3cell is %sn, classca3cell ca3contents ca3 fprintfThe class of ca3contents is %snn, classca3contents % Now lets see what gets displayed when we make use of the % celldisp function specially created for displaying cells: fprintfnHere is the thing that celldisp returns:n celldispca;
One utilization of cell arrays would be to hold lists of strings of several lengths. Since arrays are rectangular, you cant produce an character variety of strings unless each string was the identical length or padded with blanks to get as long because the longest string. To get around that, you are able to use a cell array instead of the character array. Each cell inside cell array would hold a string of the different length - it doesn't have to all be precisely the same length like that has a character array. For example:
ca Short; A little longer; A really really long string
If you will get strange error messages while working together with cells or cell arrays, one simple thing to try is always to change your braces into parentheses, or maybe your parentheses into braces, to see if that eliminates the errors.
Its also possible to blend indexing with the row and column with the cell array while using indexing in the contents in the single cell at this row and column with the cell array. For example, lets make a cell range of 2 rows and 3 columns, plus in every cell of the lets put a 4 element integer array. Then well access the 2nd element from the integer array with the cell in row 1, column 2 on the cell array.
Create a clear cell range of 2 rows and 3 columns. % Each element inside the array is really a single cell. rows 2; columns 3; c cellrows, columns; % Now, per cell inside the cell array, % put several 4 random integers from the range 1-99. for column 1: columns for row 1 : rows randomNumberArray randi99, 1, 4; crow, column randomNumberArray; % An alternate strategy for specifying is given within the next line. %crow, column randomNumberArray; % Note alterations in braces and parentheses. fprintfThe integer array in row %d, column %d from the cell array row, column, randomNumberArray1, randomNumberArray2, randomNumberArray3, randomNumberArray4; end end % Print out the other element on the 4-element integer array % in the cell for the 1, 2 position of your respective 2D range of cells. ourValue c1, 22 fprintfThe second element in the integer array in cell row %d, column %d row, column, ourValue;
To visualize, imagine you had a multitude of buckets arranged into two rows and 3 columns this can be our cell array, along with each bucket are 4 billiard balls arranged in a very line. The above example visits the bucket in the primary row and second column, and reads off of the number with the second billard ball as bucket.
It doesnt. It uses full double-precision floating point numbers to calculate everything. By default it only prints some decimal places on the screen. You can change this utilizing the command:
When performing linear algebra operations on complex matrices, it will always be the complex conjugate transpose generally known as the Hermitian transpose that is required see Gilbert Strangs linear algebra book for discussion- page 293 in edition 3. The bare apostrophe can be an operator that may the complex conjugate transpose. The non-conjugating transpose operator is often a period and then an apostrophe. Type help punct to find out more.
is not corresponding to any number, not even
itself. Therefore there are 2 ways to detect
tends to become 20%-30% faster. Heres the test snippet if you need to see the comparison:
In R12 MATLAB 6.0, this really is controlled with a preference. Select the File menu item, and select Command Window within the Preferences dialog that appears. In the Display section, theres a checkbox labeled Limit matrix display width to eighty columns. Unchecking that box allows matrix displays to generate full use on the Command Windows width. Unchecked could be the default.
Starting with MATLAB R12.1, users can access the existing command window size with all the root property CommandWindowSize. That is,
In R12.0, there is no method to do this if you don't call undocumented C functions at a MEX file.
Starting in MATLAB 7 R14, the syntax is:
You also can highlight a bit of code and type control-r to comment your code - this will likely place a percent symbol % for the beginning with the line. Typing control-t will uncomment the lines by removing any percent symbol that would be the first non-blank character within the line.
If you possess an older version, the built-in editor in MATLAB 6.0 includes a block-comment feature, that will simply put a comment character on each line. Or you can make use of matlab-mode for Emacs, which assists to this at the same time.
If that you are using an even older version, take advantage of this:
This isn't the best solution, since parse errors inside that block can cause an error.
The key would be to create a startup.m file. Look in the online help for more in depth instructions specific on your operating system.
You can make use of the following one-line function to discover the indices from the local maxima.
If there is a Image Processing Toolbox, you can makes use of the imregionalmax function. If you will find the Signal Processing Toolbox you can make use of the findpeaks function.
You could have used a flexible called i earlier inside your program or session, thus overwriting the imaginary constant i with your own individual number. In this situation, MATLAB use your new value for i as opposed to treating i as sqrt-1. Five strategies to ensure that you get a complex result are:
Use the syntax 6i; MATLAB always interprets this as 6sqrt-1
Note: they're very good causes of not using i j as indexes in FOR loops, by way of example
Easiest solution: make use of the PATHTOOL GUI. Or if you need command line access:
Suggested by Joshua Stiff: You are able to use addpath to feature directories on the command line, and path2rc to write the existing path to pathdef.m. If you don't have write permissions for pathdef.m, path2rc can write to some other file, that you can execute out of your startup.m.
R14 - Matlab 7.0 - MCR 7.0 - compiler 4.0 - R14SP1 - Matlab 7.0.1 - MCR 7.1 - compiler 4.1 - R14SP2 - Matlab 7.0.4 - MCR 7.2 - compiler 4.2 - R14SP3 - Matlab 7.1 - MCR 7.3 - compiler 4.3 - R2006a - Matlab 7.2 - MCR 7.4 - compiler 4.4 - R2006b - Matlab 7.3 - MCR 7.5 - compiler 4.5 - R2007a - Matlab 7.4 - MCR 7.6 - compiler 4.6 - R2007b - Matlab 7.5 - MCR 7.7 - compiler 4.7 - R2008a - Matlab 7.6 - MCR 7.8 - compiler 4.8 - R2008b - Matlab 7.7 - MCR 7.9 - compiler 4.9 - R2009a - Matlab 7.8 - MCR 7.10 - compiler 4.10 - R2009b - Matlab 7.9 - MCR 7.11 - compiler 4.11 - R2009bSP1 - Matlab 7.9.1 - MCR 7.12 - compiler 4.12 - R2010a - Matlab 7.10 - MCR 7.13 - compiler 4.13 - R2010b - Matlab 7.11 - MCR 7.14 - compiler 4.14 - R2011a - Matlab 7.12 - MCR 7.15 - compiler 4.15 - R2011b - Matlab 7.13 - MCR 7.16 - compiler 4.16 - R2012a - Matlab 7.14 - MCR 7.17 - compiler 4.17 -
You can offer multiple functions defined within a m-file, nevertheless, you cant use a script accompanied by one or more functions in the identical m-file. For example, this m-file:
This could be the m-file called test.m, composed of an script as well as a function. % It will generate one. clc; % Clear the command window. m magic7; MyCustomFunctionm % Define a custom function inside m-file function MyCustomFunctionm dispm;
because lines 1-5 undoubtedly are a script, and 7-9 undoubtedly are a function. To fix, convey a function line as the very first line inside your code after any comments and it'll work. See below:
This could be the m-file called test.m made up of two functions. function test clc; % Clear the command window. m magic7; MyCustomFunctionm % Define a custom function from the m-file function MyCustomFunctionm dispm;
If you lack that function line, its a script, therefore you cant then define functions later further down with your code. By adding that line, you will be making a function out with the first few script lines as part of your m-file, when all code is within functions, there isn't a error.
Please dont accomplish this! You will find that MATLAB arrays either numeric or cell enables you to do the identical thing inside a much faster, a lot more readable way. For example, if A1 through A10 contain scalars, use:
A zeros1, 10; % Not necessary, just considerably faster for i1:10 Ai % some equation end
Now consider Ai any time you mean Ai. In case each Ai boasts a vector or matrix, each that has a different size, you desire to use cell arrays, that happen to be intended exactly due to this:
Note that many Ai boasts a different size matrix. And be careful to utilize the curly braces to the subscript!
Another strategy to have your cake and eat it too would be to use structures as an alternative to cell arrays. The fields from the structure would be the variable names you desire. And you'll be able to index into them dynamic field references. For example:
names fred sam al; for ind 1:lengthnames s.namesind magiclengthnamesind; end
In this situation, you end up using the variable s, a structure, containing fields specified from the strings stored inside the cell array names.
Now, should you still really need to create variables with dynamically generated names, you need make use of EVAL. With EVAL, you utilize MATLAB commands to get the string that could perform the operation you're planning. For example, evalA10 has the identical effect as A10, and evalA B 10 has precisely the same effect as AB10, exactly the EVAL method executes additional slowly. So in the loop, you could utilize:
Notice how far more obfuscated that is. In addition, this will cause difficult-to-troubleshoot problems inside your code, particularly when you try to dynamically develop a variable together with the same name as being a function:
Calling this function with y mysin1 will never return y 5 the initial element with the sin variable put together by EVAL - - it is going to return the sine of just one, because in the event the function was parsed there were no variable named sin therefore, the usage of sin within the last line was parsed like a call for the built-in SIN function. The fact that an adjustable named sin existed at runtime is irrelevant; the parsetime decision takes precedence.
Repeat: dont create variables at runtime using EVAL if you do not have a excellent reason, like someone will give you a MAT file with 2000 variables named A1428, as an example. Even as case, you may avoid EVAL:
Assume the MAT-file contains 2000 variables, A1 through A2000 S ; % S has become a struct array with 2000 fields, S.A1 through S.A2000. % To access A1428, use: x1 S.A1428; % If the index on the variable you wish to access is stored in the variable: k 1428; x2 S.sprintfA%d, k; x3 S.A, num2strk;
If the files that you would like to process are sequentially numbered, like, , , etc. then you can make use of SPRINTF or NUM2STR to generate the filename and LOAD, IMREAD, FOPEN, etc. to retrieve the data on the file. Also note the 3 different ways of building the file name - you are able to use your favorite way.
Read files through, through, % and through Files are inside current directory. % Use fullfile when you need to prepend various other folder on the base file name. % Adapt to utilize which ever cases you will need. for k 1:20 % Create a mat filename, and load it in to a structure called matData. matFileName, k; if existmatFileName, file matData loadmatFileName; else fprintfFile %s will not exist.n, matFileName; end % Create a perception filename, and focus it in to a flexible called imageData. jpgFileName strcatimage, num2strk, ; if existjpgFileName, file imageData imreadjpgFileName; else fprintfFile %s won't exist.n, jpgFileName; end % Create a text file name, and browse the file. textFileName file num2strk ; if existtextFileName, file fid fopentextFileName, rt; textData freadfid; fclosefid; else fprintfFile %s isn't going to exist.n, textFileName; end end
In these code, matData, imageData, and textData can get overwritten whenever. You should save them to a selection or cell array in the event you need make use of them beyond your loop, otherwise make use of them immediately in the loop.
The second method is if you would like process each of the files whose name matches a pattern inside a directory. You can utilize the DIR function to return a summary of all file names matching the pattern, one example is files or files, or all files named where nnnn is really a number. Note that even if this example uses because pattern and IMREAD to read inside data, as with all the previous example you can use whatever pattern and file reading function suits your applications needs:
Specify the folder the location where the files live. myFolder C:UsersyourUserNameDocumentsMy Pictures; % Check for making sure that folder actually exists. Warn user if this doesnt. if isdirmyFolder errorMessage sprintfError: The following folder will not exist:n%s, myFolder; uiwaitwarndlgerrorMessage; return; end % Get a directory of all files inside the folder with all the desired file name pattern. filePattern fullfilemyFolder, ; % Change to whatever pattern you may need. theFiles dirfilePattern; for k 1 : lengththeFiles baseFileName ; fullFileName fullfilemyFolder, baseFileName; fprintf1, Now reading %sn, fullFileName; % Now do whatever you would like with this file name, % like reading it in as a graphic array with imread imageArray imreadfullFileName; imshowimageArray; % Display image. drawnow; % Force display to update immediately. end
Or you can utilize simpler, though quite a bit less robust, code inspired with that StackOverflow question:
csvfiles for file csvfiles fprintf1, Doing something end
The simplistic code above assumes that files will be inside the current folder. Or you'll be able to try a File Exchange Pick with the Week: FileFun.
In MATLAB all array indices has to be logical or positive numeric integers. This means that this is permitted:
A3.14159 % 3.14159 isn't an integer Subscript indices must either be real positive integers or logicals.
A0 Subscript indices must either be real positive integers or logicals.
A-1 Index exceeds matrix dimensions.
Note that fractional numbers, negative integers, zero, and complex/imaginary numbers usually are not permitted indices. Note that zero is permitted for an index if it is not really an integer or double zero, however , false - may well data type. When MATLAB displays logical values it uses 0 and 1 in lieu of false and true.
The reason is the fact that the indexes make reference to rows and columns inside array. So while you might have row 1 or column 3, you cant have row 3.14159, nor can there is the 0th row or column, or - 1th row or column.
To fix the big mistake you must ensure your indexes are true, positive integer numbers, or logicals. They could be scalars single numbers or vectors or arrays of the many numbers. You might make expression for the index and produce it in to a single variable, like myIndexes, after which examine that inside the variable editor or use code similar to this to figure out its real data type and value:
myIndexes some complicated expression format long myIndexes % No semicolon so will print directly on the command line. whos myIndexes % Displays data type, int32, double, logical, structure, etc.
You cannot mix a script and operations in a similar m-file. You may have a script, and this script can call functions in other m-files, or you may have all functions without script in any way. Most likely you've forgotten to incorporate the function keyword as well as the name within your m-file as the initial executable line of your respective m-file. If you do that, it'll probably work. See this examples:
This test.m posesses a script and also a function, SomeFunction. % You can not do that. It will not work when you % cannot mix a script having a function in the identical m-file. % You will obtain the error Function definitions usually are not permitted with this context. % If SomeFunction were in a very separate m-file, SomeFunction.m, % as an alternative to in a similar m-file, test.m, it would work. % Here would be the script: clc; % Clear the command window. workspace; % Make sure the workspace panel is showing. format compact; m randi9, 2, 3 output SomeFunctionm % Here will be the function: function output SomeFunctionm output 2 m; % Multiply m by 2.
This test.m contains two functions: ensure that you SomeFunction % You can make this happen. Because it just has functions, % and does not have a very script, it truly does work. % Because the 1st executable type of code is function test % that turns it from your script in a function and allows results. % Here will be the first function, that gets the name in the m-file: function test % -- Key function definition keyword! clc; % Clear the command window. workspace; % Make sure the workspace panel is showing. format compact; m randi9, 2, 3 % Define sample data. output SomeFunctionm % Call SomeFunction % Here would be the second function. It should not take within the name % associated with a built-in MATLAB function to stop conflict. function output SomeFunctionm output 2 m; % Multiply m by 2.
Note: in the event the name from the first function declared inside the m-file doesn't match the file name, it can execute when called because of the file name, not the name following your function keyword. For example, inside the second example above, whenever we had improperly known as the function TestFunction
then a code would execute by issuing the command test because thats the name on the m-file. Issuing the command TestFunction would give larger than fifteen Undefined function or variable testFunction.
Yes. If the file has nothing but numbers separated by whitespace, and has now a constant volume of columns car file, you are able to just type load
The function DLMREAD is much more flexible and allows you you just read files with fields delimited by any character.
If you've mixed data, including columns of text and numbers, you can make use of READTABLE. The first line may be the column headers line and says the fields in the table will likely be called.
The function TEXTREAD is much more flexible still and permits you to skip lines in the beginning, ignore certain comment lines, read text along with numbers, plus much more. Type help textread to learn more.
If you are working with a more difficult file try XLSREAD, for instance when opening a csv file with only partially numerical content.
If none of those suit your needs, it is possible to always make use of the low-level file I/O functions FOPEN, FREAD, FSCANF, FGETL, FSEEK and FCLOSE to read the details however you need.
1 Using globals is perfectly okay thats why they're there in beginning, much like fors and whiles and also other intelligent 2nd generation computer language constructs that MATLAB was made on, as long as you happen to be careful about where, why, and how you utilize them.
2 However, using globals is just not recommended by many programmers given it shows that she/he didnt think ahead but was rather and merely kept adding on those never-ending important build parameters that she/he needed make use of by every one of the axes - or whatever - of the one single project.
3 Using globals can generate problems in terms of bookkeeping in case you end up having a large number of them hovering around with your workspace. If you happen to be not careful and utilize the same names for global variables that represent something more important, then you might start having problems in the event the global myParameter from function1 is mixed up with all the global myParameter from function2. You are able to do whos global to show you the many global variables.
4 A nice approach to reduce the variety of global variables is usually to collect your complete globals to a single structure thereby uncluttering your workspace. For example
Declare UserSettings or whatever name you wish as global on this function. global UserSettings; % Get the user folder in the user who logged in towards the computer. userFolder getenvUSERPROFILE % C:UsersYourName % Set up global variable, UserSettings, to be used in any function that % declares UserSettings as global, in ONLY those functions. fullfileuserFolder, Documents , Results 42pi;
Just attach any variables that you simply want to create global for the UserSettings structure. Now, another function that declares UserSettings as global will have use of all on the member fields of UserSettings. Other functions that do not contain the global UserSettings line in them will not likely be able to begin to see the UserSettings global variable. It isn't global unless the international line is included inside function.
5 Alternatively you may not have UserSettings as global and instead pass it for an input argument just to those functions that want it. This is one preferred method of sharing variables in plus it shows your intelligence, as well.
If youre using global variables because you wish to share variables between functions, look in the section on How can I share information between callback functions during my GUI. That part of this FAQ lists some choices to using global variables.
The logical vectors made out of logical and relational operations enables you to reference subarrays. Suppose X is undoubtedly an ordinary matrix and L can be a matrix in the same size that would be the result of some logical operation. Then XL specifies the sun and rain of X the place that the elements of L are nonzero.
Ive discovered to my horror that structs undertake an obscene volume of overhead Im running version 5.3.1.29215a R11.1 with a Dec ALPHA. I have a number of 10, 242 observations, each comprising 31316 fields, who have 327 113 94 values. So the total size in bytes needs to be 10, 242 94 8 bytes/double 7, 701, 984.
I have this stored in a very 1 x 10242 data structure, and once I issue the whos command, it tells me that your data now uses up 27, 367, 136 bytes!
My guess is that their a structure contains MATLAB arrays. Each array has some overhead, like data type, array sizes, etc. In your second implementation index using observation, you will find 10, 242 times less arrays allocated. Note that inside your data, for every single observation, you've 13 arrays with one value. I have no idea how large the matrix header exactly is, but it is often a waste putting a single value inside it!
I think Cris has hit it exactly. Every MATLAB matrix has a overhead of 100 bytes, even matrices using a single element. In this example, you will find 16 fields 10242 elements 163872 matrices. Each one these matrices adds an extra 100 bytes, for 16.4Mbytes in pure overhead. This still happens a little short with the amount reported, yet it's fairly close.
It is additional efficient, both for storage and computation, to utilize a struct of arrays rather than numerous structs.
Memory errors is one likely reason. Greg Wolodkin suggests the debug memory manager:
The platform-independent solution to use the debug memory manager should be to set environmental surroundings variable MATLABMEMMGR to support the string debug.
The debug memory manager cannot catch your code the minute it writes away from bounds tools like Purify can do that but the performance hit they induce is pretty painful. What it is going to catch is the fact that in general, whenever you write beyond one memory block you finish up writing into another, corrupting it or within the case on the debug memory manager hopefully corrupting simply a guard band. When you later free the memory, we could tell you that you just walked off of the end from the block and corrupted the guard band.
In many programming languages, boolean operators like AND and OR stop evaluating as soon because the result is known. For instance,
would never get to your error part, because the 1 is usually true.
In older versions of MATLAB, the boolean operators and they are only short-circuit evaluated within the conditions of IF and WHILE statements. In all other contexts, all parts with the conditional are evaluated.
A frequent variant of the question is: I have 3 GB of RAM, and a couple GB of swap space. Why cant I create this 600 MB matrix?
First of the, issue the command memory inside the command window to determine how much memory can be obtained on your computer. It should return something this way:
Maximum possible array: 520 MB 5.457e008 bytes
Memory readily available for all arrays: 1343 MB 1.409e009 bytes
Memory made use of by MATLAB: 447 MB 4.690e008 bytes
Physical Memory RAM: 3036 MB 3.184e009 bytes
Remember that double precision floats undertake 8 bytes. So millions of element vector consumes 8Mbytes. Be sure youre estimating properly.
Many operations need to make duplicate matrices. For example, B invA. must produce a tempory variable the identical size as A to support the transpose, and B may be the same size as A.
Another variant of the question is: How do I pre-allocate memory whenever using MATLAB?
If the matrix size is just not defined previous to populating it with data by using a FOR loop, memory fragmentation problems may occur since MATLAB just isn't aware on the final matrix size upon the conclusion with the FOR loop. In order to figure around this concern, one solution would be to pre-allocate memory by creating a first matrix of zeros together with the final size with the matrix being populated inside the FOR loop. You should read the subsequent Mathworks article: Technical Solution 1-18150 for the more complete discussion in this problem.
fname foobag; save fname variable;
To try this correctly, you would like to makes use of the functional sort of save:
fname foobar; savefname, variable;
In fact, it can be true normally that this two lines are equivalent:
command str1 str2 str3 commandstr1, str2, str3
This allows one replace any or all in the parameters with dynamically generated strings. This is also valuable in commands like PRINT, LOAD, CLEAR, etc.
M-files are plain ASCII text that may be interpreted at run time. Actually it can be parsed once and merely-in-time compiled, but that is transparent towards the user. Use M-files for most of the MATLAB development, and then for platform independence and maintainability.
Pcode is often a preparsed and encoded version in the M-file. Since it can be preparsed, it saves around the load time in the function. This is that's doubtful an issue apart from very large M-files, since the majority of are parsed only one time anyway. Pcode also helps you to hide the origin code from others. Careful, there is no solution to convert Pcode back on the M-file source. Pcode is platform independent.
MEX files are native C or C files that happen to be dynamically linked directly in to the MATLAB application at runtime. They should be compiled for each and every hardware architecture on which these are to be run. MEX files possess the potential to crash the MATLAB application, but alternatively large speed gains are possible, depending around the algorithm.
Handle objects do exhibit reference behavior when passed as function arguments; value objects don't. When you pass a handle mind a function, MATLAB still copies the value from the argument towards the parameter variable inside function with one dose of subtlety; see below. However, all copies of the handle object talk about the same underlying object.
If a function modifies a handle object passed just as one input argument, the alteration affects the article referenced by their original and copied handles. In it, the function won't need another the result for being reassigned.
If instead you might be attempting to utilize pass-by-reference to protect yourself from unnecessary copying of information into the workspace on the function youre calling, you must be aware that MATLAB relies on a system commonly called copy-on-write to avoid building a copy on the input argument from the function workspace until or if you do not modify the input argument. If you tend not to modify the input argument, MATLAB will avoid setting up a copy. For instance, in this particular code:
function y functionOfLargeMatrixx y x1;
MATLAB won't make a copy from the input inside workspace of functionOfLargeMatrix, as x isn't being changed because function. If for the other hand, you called this function:
function y functionOfLargeMatrix2x x2 2; y x1;
then x will be modified within the workspace of functionOfLargeMatrix2, and for that reason a copy have to be made.
The term function functions identifies functions in MATLAB and also the toolboxes that accept a function normally a function handle and evaluate that function repeatedly during their work. Some samples of function functions are:
the ordinary differential equation solvers like ODE45, ODE23, etc.
the optimization functions from the funfun directory in MATLAB, like FMINSEARCH and LSQNONLIN
the optimization functions within the Optimization Toolbox, like FMINCON, FSOLVE, and LSQCURVEFIT
the optimization functions within the Genetic Algorithm and Direct Search Toolbox, like GA and PATTERNSEARCH
There are many documents on The MathWorks support website that shows types of how to secure additional parameters towards the functions used from the function functions.
When a function is cleared from memory while using CLEAR function, breakpoints for the reason that file may also be cleared. That means that should you execute code for example the statement clear functions, pay off the name of your respective function, or clear all, your breakpoints is going to be cleared.
If you need to have your program stop execution and enter debug mode whether or not or not you could have cleared it, insert a call to your KEYBOARD function into your code on the location where you need to enter debug mode. This won't be cleared through the CLEAR function and can cause MATLAB to penetrate debug mode if the KEYBOARD function is named.
Alternately, you can makes use of the Stop if Errors/Warnings item in the Debug menu inside the MATLAB Editor to cause MATLAB to go in debug mode whenever the code youre running throws a mistake that will not be caught using a TRY/CATCH block, whenever it throws an oversight that is caught by way of a TRY/CATCH block, whenever it throws a reminder, or whenever the value of any variable becomes Inf or NaN. You can find more information on this item within the documentation .
One prevalent reason for an Undefined function or variable error or even an error concerning the RecursionLimit being exceeded when utilizing an ODE solver like ODE45 is the function being called with the ODE solver itself is the call for the ODE solver. For instance, if the code is:
function dy myodefunctiont, y dy y2; 2t; y0 0; 1; tspan 0 10; t, y ode45myodefunction, y0, tspan;
If you call myodefunction without any inputs, you'll receive an error for the second line, where MATLAB tries make use of t and y to define dy. If you call myodefunction with two inputs, it is going to proceed without error on the ODE45 call. ODE45 will call myodefunction with two inputs, knowning that call will proceed without error to your ODE45 call. This process will repeat until ODE45 has recursively call myodefunction a quantity of times equal on the root RecursionLimit property, at which MATLAB will throw an oversight.
To avoid these errors, will not include the call for the ODE solver with your ODE function the function you pass towards the ODE solver as the primary input argument. Instead, define the ODE function in a very subfunction or being a separate function file and rehearse that with your ODE45 call.
begin myodefunction.m function t, y myodefunction y0 0; 1; tspan 0 10; t, y ode45myodesubfun, y0, tspan; function dy myodesubfunt, y dy y2; 2t; % end myodefunction.m
begin myodefunction.m function t, y myodefunction y0 0; 1; tspan 0 10; t, y ode45myodeseparatefun, y0, tspan; % end myodefunction.m
begin myodeseparatefun.m function dy myodeseparatefunt, y dy y2; 2t; % end myodeseparatefun.m
The EVAL function is one on the most powerful, flexible, and very dangerous functions in MATLAB. Since EVAL is very powerful, it truly is easy to misuse the function. In a way, the EVAL function is really a lot like global variables; they are both tools which can be so easy to make use of that it could possibly be easier make use of them as opposed to to search for any more elegant, safer, and appropriate solution. There is usually a major drawback on the EVAL function, eventhough it can be avoided in case you use EVAL carefully. EVAL enables you to alter arbitrary variables. In addition, two related functions, evalin and assignin, enable you to alter variables in numerous function workspaces. These functions can cause bugs which might be difficult to reproduce and extremely hard to eliminate. Further explanation, and The Mathworks official warning against using eval, might be found in Mathworks Tech Note 1103.
Sometimes when you writing code that does file input/output without specifying the total path folder base file name you will possibly not find your file. It may cease there you just read in or may cease written out to your folder you expected. For example
storedStruct ;
If another function call used the cd function to change the actual folder, you would be looking to this folder whenever you tried to read in the file or find out a file. If you thought you were looking at some other folder, then youll have a file not found error upon attempting to read in a very file, if not not chose the file for the reason that folder that you just thought you wrote to. It would be best if any code that used cd saved and restored the main folder:
originalFolder pwd; % Do stuff. Then restore the main folder cdoriginalFolder;
however you cannot always are based upon that. Its much, far better to not use cd and instead create the entire-blown explicit filename with functions for example sprintf, fileparts, and fullfile. Because if there is the full path name in the file, youll know for several where it is going to get saved to or read from. See the subsequent code for guidance:
Code must user for just a folder. startingFolder pwd; returnValue uigetdirstartingFolder, Select folder; % returnValue will likely be 0 a double should they click cancel. % returnValue are going to be the path a string when they clicked OK. if returnValue 0 % Assign the value as long as they didnt click cancel. folder returnValue; else folder startingFolder; end % Example 1: Write out file by incorporating variables. % Create the entire file name. baseFileName ; fullFileName fullFilefolder, baseFileName; % Save your variable to the mat file. stringToSave It is risky to make use of cd.; % Some sample variable. integerToSave 42; savefullFileName, stringToSave, integerToSave; % Example 2: Read in a very mat file baseFileName ; fullFileName fullFilefolder, baseFileName; if existfullFileName, file % It exists. storedVariablesStructure loadfullFileName; else % It doesnt exist. warningMessage sprintfError reading mat filen%s.nnFile not fullFileName; uiwaitwarndlgwarningMessage; end
Unlike custom functions that you simply write, the callback functions make predetermined input variables hObject, eventdata, handles so it isn't clear how you are able to pass in other variables that you may need to. There are a few techniques you may use to share information between callback functions with your GUI. Which approach is easiest is dependent upon whether you're creating your GUI using GUIDE to design layout, design GUIDE-based GUIs or whether you might be calling FIGURE, AXES, UICONTROL, etc. directly programmatic GUIs.
Using the handles structure. You can dynamically additional new members for the handles structure that have your variables that you wish to pass in. Unlike global variables, which expose the variables only that you put the worldwide statement, attaching towards the handles structure and passing handles will share every one of the variables you've got attached to your handles structure. This could expose variables in your function which you did not need or want exposed. Since variables passed in MATLAB functions are ignore value and not overlook reference in the event you change any from the variables, you're only changing the neighborhood copy. If you change any with the variables attached as members on the handle structure, and you would like to retain these changed values inside calling function, you will should return the handles structure just as one output within your function, and accept it inside your calling function, or else utilize guidata function. Otherwise changes you make to your handles structure variables are simply local and will not likely survive as soon as the function has returned.
Add the latest variable on for the handles structure. 42;
Creating your callback functions as nested functions in the main GUI function. The function has to be truly nested together with the main functions end statement and never merely listed as another separate, independent function just defined within the m-file. There can be a difference.
Storing data within a property usually the UserData property of an component from the GUI and retrieving it as you desire. For example
1, UserData, myString.
Storing data from the application workspace utilizing the SETAPPDATA and GETAPPDATA functions.
Do this to save lots of variables for a figures workspace. % will be the Tag property of your respective main GUI figure. % Double-click the figure to create up the Property Inspector in GUIDE % to discover what your figure known as. You could have called it different things % than GUIHandle. You can it is known as whatever you need but the name within the tag % field in the Property Inspector must match the name in setappdata., yourVariable, yourVariable % Do this to retrieve variables out of your figures workspace. yourVariable, yourVariable % Do this to take out what you saved from the figures workspace., yourVariable
Declaring the variables global. For example, in case you have this in the function:
global myVariable; % Declare global. Any function on this line it it could see this variable.
then some other function that also has got the global myVariable declaration in it'll be able to start to see the variable called myVariable. Functions that do not develop the global myVariable line in them won't be able to view the variable. So its actually much more a friend variable if youre informed about C programming when compared to a truly global variable because you cannot assume all function or workspace sees it. The myVariable variable won't be seen from the base workspace - it'll be seen only inside functions together with the global myVariable declaration in the individual.
Writing your data out to personal files, like a mat file while using save function, after which having the called function read as mat file.
Do this in order to save variables in your figures workspace. % yourVariable is actually a single variable that is usually a structure % using a bunch of variables as members from the structure % in the event you wish. That is usually convenient because then there % is just one variable to avoid wasting. savefullMATFileName, yourVariable % Do this to retrieve the variable. storedStructure loadfullMATFileName; yourVariable ;
Use the assignin function.
Send the variable myGUIVariable on the GUIs workspace % to an adjustable called myBaseVariable inside the base workspace. assigninbase, myBaseVariable, myGUIVariable; % They could both be exactly the same name in case you wish. assigninbase, myVariable, myVariable;
Sharing between multiple GUIs. If the main GUI calls other GUIs, next the best strategy to do it truly is by passing variables in through the input argument list, and accepting output variables through output argument list. The output argument of GUI2 might be sent into GUI3. So someplace in GUI1 such as callback function from the Go! button of GUI1, youd have this
out2a out2b out2c gui2in2a, in2b, in2c, in2d; out3a out3b gui3out2a, out2b;
or something along those lines. The arguments may be extracted out with the varargin cell assortment of your opening code for that GUI, for example inside GUIs OpeningFcn function in case you used GUIDE. Once these are in your opening function, then they may be shared among the other functions inside the GUI while using methods mentioned earlier within this section. This method will not likely let GUI1 control GUI2 and GUI3s parameters live - they is usually changed only if calling the GUIs. To have GUI1 control GUI2 when GUI2 is definitely running, you can utilize assignin function.
Official Documentation. The documentation contains instructions for implementing these techniques to share information between callbacks over these Mathworks webpages:
The ticklabel gets its properties in the axis to which it's attached. So setgca, fontsize, 14 should perform trick. Type getgca to view what else it is possible to set.
Not MATLAB isn't going to interpret TeX strings in ticklabels. You can play games with placing text yourself. See the MathWorks solution for a lot of ideas of the best way to work with this in mind.
There will also be some free third-party software programs you are able to use to make this happen. One community-generated solution inside the MATLAB File Exchange is Format Tick Labels ?objectId15986 for an example. It will replace axes tick labels with formatted text objects which could include both Tex and LaTex interpreted strings.