Simulink Matlab Function block
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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.
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Accepted Answer
Niklas Nylén
on 18 Dec 2013
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
3 Comments
Sinan Ibrahim Bayraktar
on 16 Mar 2019
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
on 13 Oct 2020
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);
More Answers (2)
Rubem Pacelli
on 1 Aug 2019
Edited: Rubem Pacelli
on 1 Aug 2019
There are another solution for your question.
- Double-click in the MATALAB function block. Will open a script function of your "MATALAB function" block
- click on edit data
- click on add -> data (or just type cntrl+D shortcut keyword)
- type the same name of the variable tha you want pass to MATLAB function block
- In Scope, choose "Parameter" option.
It's work fine in my computer. You need save your variable in the MATLAB workspace.
5 Comments
mohammad nojavan
on 20 Aug 2020
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
elec.engeen2011@gmail.com
Sunandan Adhikary
on 7 Feb 2021
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.
Ryan Livingston
on 18 Dec 2013
You may want to add the variable as an input parameter under the ports and data manager:
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.
3 Comments
Ali Mukhtar
on 12 Sep 2019
Edited: Ali Mukhtar
on 12 Sep 2019
hi how can access the values of variables written in simulink function block?
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