How can I assign a value to a variable in the first iteration of a loop and for the rest of iterations the variable's value should be the outcome of the script?

I have a simple script that will calculate the value of the variable 'y' depending on the values of the variables 'u' and 'v':

function y = fcn(v,u)
y=0;
if (u>v)|| (u<v) 
    y=y+(u-v);
else
    y=y;
end

For the first iteration, the initial value of 'y' should be zero. For the rest of iterations, the initial value of 'y' should be the 'y' value of the previous iteration. How can I specify it in the script?

[Erik]

I forgot to mention that I'm writing the script in a Matlab function block in Simulink.

Answer 1

[David Young]

Make y an argument to your function, and also remove unnecessary code:

function y = fcn(v, u, y)
  y = y+(u-v);
end

Note that you didn't need the test, because if u is the same as v, u-v is zero.

Then in the calling code, initialise y to 0 before entry:

y = 0;
for k = 1:n
  y = fcn(v, u, y);
end

[Erik]

Thank you for your answer David. I'm running this script in Simulink, so the limits of the 'for' loop will depend on the simulation time. How can I specify that?