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matlabsimulink

How can i save previous value of variable in Matlab Function

Hello I would like to know how to save the previous value of an output variable in a matlab function.

function y = fcn(x,d,yp)
yp=0;  %here I want to initialize this value just at the start of simulation
if (x-yp<=d)
    y=x;
else 
    y=yp + d;
end
yp=y;  % here i want to load output value

Thanks for your help

Solution

  • Using a persistent variable is the correct way to go, but as you found out, you cannot use varargin in a MATLAB Function block. The trick is to check whether the variable is empty or not, as in:

    function y = fcn(x,d,yp)

persistent yp

if isempty(yp)
   yp=0;  %only if yp is empty, i.e. at the beginning of the simulation
end

if (x-yp<=d)
    y=x;
else 
    y=yp + d;
end

yp=y;  % here i want to load output value