Simulink Matlab Function block

I have a Matlab workspace variable called clock_frequency.

I use this variable as a parameter in many of my simulink blocks.

I want to be able to access and alter this variable within my Simulink Matlab Function block, but I cannot do it successfully. Unlike the other simulink blocks (that can see the workspace variables) the matlab function block cannot.

I do not want to create a port and pass the variable in as a signal for various reasons.

Reading through the documentation, I have to use data store memory, but this doesn't seem to work. I got a partial version of this working, and the simulink model began running really slowly.

Answer 1

[Niklas Nylén]

This function will read the value x from the base workspace, add 3 to it and write back the new value to the workspace as x. On the next iteration it will read the new value of x and so on.

function y = fcn()
%#codegen
coder.extrinsic('evalin', 'assignin')
x = 0;                  % Needed in order to set variable class correctly
x = evalin('base','x'); % Read value from workspace
y = x+3;                
assignin('base','x',y); % Assign value back to workspace

[Jeremy]

Brilliant. Thanks. I learn new tricks every day! I really appreciate the help.

[Sinan Ibrahim Bayraktar]

I get an error while using it for a maxtrix. Is there a way to access this matrix even if I don't want to change it?

[N/A]

I believe you could define the matrix with zeros before using 'evalin'. For instance, if you want to import a matrix 'x' that is 2X3 in size, define the following in place of fourth line above.

x=zeros(2,3);

Answer 2

[Rubem Pacelli]

There are another solution for your question.

1. Double-click in the MATALAB function block. Will open a script function of your "MATALAB function" block
2. click on edit data
3. click on add -> data (or just type cntrl+D shortcut keyword)
4. type the same name of the variable tha you want pass to MATLAB function block
5. In Scope, choose "Parameter" option.

It's work fine in my computer. You need save your variable in the MATLAB workspace.

[Timothy Reilly]

Thanks Rubem,

I was struggling so much trying to find a way to do this. This was exactly what I needed to do.

By the way it doesn't seem to like cell arrays, but it seems to work with matracies of type double. Thanks again for posting this.

Tim Reilly

[Jianye Xu]

Thanks, this is a really good way, it helped me solve my problem.

[Marlon Trujillo]

What about the Interpreted Functions? I cannot see the "data" option there...

[mohammad nojavan]

hi rubem i dowloaded a simulink file from internet tath contaies some of " Data store Memory block's" . if i want to change the value of this block they dont change and when i run the simulink file the value of data store memory blocks comeback the initial values. please help me

[e-mail]

[Sunandan Adhikary]

This way we n import the variable but it does not get updated! I am trtying to update arrays in a structure and everytime it enters the function it updates that particular indexec position but later when the function is called in next iteration, those values are gone from the array.

Answer 3

[Ryan Livingston]

You may want to add the variable as an input parameter under the ports and data manager:

http://www.mathworks.com/help/simulink/ug/matlab-function-block-editor.html#bqgwvsq-1

http://www.mathworks.com/help/simulink/ug/parameter-arguments-in-matlab-function-block-functions.html

It will show up in the function block as an input argument like:

 function y = fcn(u)

where 'u' will be the parameter name you choose. Then it will search through the workspaces as described in the second link.

[giulio zamboni]

Hi, and supposing I need also to modify the matrix or array I am passing to the function, how can I do?

I would like to read and write an array in the workspace from my matlab function.

Thanks

[Ali Mukhtar]

hi how can access the values of variables written in simulink function block?

[Marlon Trujillo]

This is limited to some types of variables...