MATLink

Connecting to MATLink

To launch MATLink and begin communicating with MATLAB, execute the following in a notebook:

Needs["MATLink`"]
OpenMATLAB[]

Throughout the rest of this guide, it is assumed that you're connected to MATLink and the MATLAB workspace is open.

Executing MATLAB commands

You can execute arbitrary MATLAB code using the MEvaluate command. Any output that would normally be displayed in MATLAB's command window will be displayed in the output cell. For example, evaluating

MEvaluate["mat = magic(4)"]

will output a magic square of size 3 and make an assignment to a variable named mat in the MATLAB workspace. Think of MEvaluate as a portal to the MATLAB workspace, allowing you to run commands in it and assign values to variables.

MEvaluate, when successful, will always return a string containing the output from MATLAB's command window. It cannot be used to transfer data to Mathematica. Use MGet and MSet as explained in the next section.

Transferring data between Mathematica and MATLAB

The functions MSet and MGet allow the user to transfer variables to and from the MATLAB workspace. The variable name is always passed as a string. For example, to transfer the data stored in the variable mat in the MATLAB workspace to Mathematica, evaluate

mat = MGet["mat"];

Now let's transform this variable in Mathematica and send it back to MATLAB:

MSet["mat_tr", Transpose[mat]];

You can verify that a new variable mat_tr was created in the MATLAB workspace and has the correct value:

MEvaluate["
exist('mat_tr','var')
isequal(mat', mat_tr)
"]

Since MATLAB is white space insensitive, you can freely use newlines and indentations for clarity in MEvaluate's argument. Lines not terminated by a semicolon will display the output in Mathematica.

Working with scripts and functions

Often one wishes to reuse code found online, either on the MathWorks File Exchange or elsewhere and execute it as a script (i.e., in the base workspace and not as a function). The function MScript makes it easy to do this. As a simple example, we'll define a script called timing.m that does some computations using the two variables mat and mat_tr defined earlier and displays the timing for 1000 trials:

t = MScript["timing",
"tic;
for i=1:1000
eig(mat*mat_tr);
end
toc"
]

You can now run the above script anytime, several times within the current session, by evaluating MEvaluate[t] (assuming the value for t has not been cleared) or MEvaluate[MScript["timing"]] (this will work even if t is cleared).

Trying to define an MScript with the same filename twice in the same MATLink session will throw an error. This is to avoid accidental overwrites. You can force an overwrite of the existing file with the option "Overwrite" -> True for MScript

You can also natively call MATLAB functions already on its path using the MFunction command. As an example, we'll define and use the magic function from MATLAB, which is not available in Mathematica:

magic = MFunction["magic"];
magic[4] // MatrixForm

To define a custom function for the current session and use it, use MScript to save it to a file (remember to use the same filename as the function) and then use MFunction["function_name"], where function_name is the name of your function file.