MATLAB: Matlab function in Simulink – calling variable from workspace

Question

Hi

I want to make a function block/iterative block, which would calculate output value depending on argument and values of some variables from previous iteration. I mean I have, for example current angle, and I subract it from prevoius value of angle. So far I used following code for Matlab Function block:

function angle= calc_angle(counter,dir)
angle = prev_angle + dir*(counter - prev_counter);
prev_angle = angle;
prev_counter = counter;

But variables with prev prefix throws errors, because they are not declared. I tried to just declare it in workspace calling function initializing them, but it haven't helped. How to deal with such calculations? Is there any way to make previous iteration's values visible to function?

Answer 1

Try declaring the variables to be persistent at the top of the function, i.e.

 persistent prev_angle prev_counter