if loop inside matlab function ----- i dont understand why this is not working

I wondered when I saw "latch" in the second comment if that might not have been OP's purpose.

"... is not possible with MATLAB function block."

While I'd never recommend for the purpose with Simulink, it is possible with Matlab by using persistent to retain state between function calls

I didn’t knew about persistent. Thanks for correction.

Hi dpb,

i want to be sure that i understood correct. The following code would work for this purpose and also would latch the value for y between the several functions calls, but is not recommended for use in Simulink?

function y = myfun(u)
persistent value
      if(u>0.7) && (u<0.71)
          value=1;
      end
      y = value;
end

Is there any reason why it should not be used this way?

best regards

Stephan

That won't latch if that's the purpose, no...as coded it will still return the value based only on the input value of u; the persistent value isn't used to determine whether or not to reset its value.

CLARIFICATION It will latch if the condition on u is satisfied, that is true; it will fail on first call for lack of value being assigned; that it has been declared persistent will keep from generating an undefined error but the function will return empty which likely will cause an error in the calling routine expecting a value.

The function would also have to be called to initialize the persistent variable first before use.

If one had need for such a function in Matlab base product that would be the way to implement it; in Simulink there's better ways given its manner of operation.

I was simply pointing out that there is (and doc says before R2006 altho I didn't think it had been that long) the facility in ML.

One (unoptimized) implementation...

function y = myfun(u,init)
  persistent value
  if nargin==2
    value=0;
    y=value;
    return
  end
  if value==1
    y=value;
    return
  end
  if u>0.7 & u<0.71
    value=1;
    y=value;
  end
end