MATLAB: How to declare a variable in the MATLAB workspace from a MATLAB function

assigninbasedeclareevalinMATLABvariableworkspace

I wrote a function that provides some variables to Simulink. I have declared them global, so Simulink could see them. But I have to declare them at the prompt and I am unable to declare them in the function because Simulink does not see them.

Best Answer

Simulink has access to any variable defined in the MATLAB workspace. You do not need to declare a variable 'global'. In order to define a variable in the MATLAB workspace from a function, you can declare the variables in the function using the command EVALIN. For example:

function declare_variable
......
evalin('base','k=100');
......

In this example, when the function 'declare_variable' is called, it will generate a variable 'k' in the MATLAB workspace. This variable can then be seen by the Simulink model. Please note that if, before the function 'declare_variable' is called, a variable called 'k' exists in the MATLAB workspace already, calling the function 'declare_variable' will overwrite the existing variable 'k' with the new value (100).

For more information on the EVALIN function, see the following URL:

http://www.mathworks.com/access/helpdesk/help/techdoc/ref/evalin.html?cmdname=evalin

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The variable might not be in the same workspace. If you defined it at the command prompt then it would be in the "base" workspace rather than in the function's workspace. You can retrieve variables from the base workspace:

   evalin('base', 'kinect_image')

but almost always a better way is to pass the variable to the function.

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This can be done using the EVALIN and ASSIGNIN commands.

function to_base_workspace()
ws=evalin('caller','whos()');
for i=1:length(ws)
tmp=evalin('caller',ws(i).name);
assignin('base',ws(i).name,tmp);
end

If you save the code above into a file named "to_base_workspace.m", you can then run the following example code:

function example
a=rand(10,10);
b='here is an example string';
c=num2cell(1:10);
to_base_workspace();

Best Answer

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