matlab - FOR loop won't complete when endval is a vector -

i have loop works fine when

n=20   (i = 1: + 1: n - 1)     disp(['iteration count =' num2str(i)])     x = p + (i * h);     fadd = f(x);     fnew = fold + fadd;     disp(['fnew = ' num2str(fnew)])     fold = fnew; end 

but when

n = [20 40]; 

the loop stops after 20 iterations , missing 20 further fnew values when n=40. or when

n = [40 20] 

the loop stops @ 40 iterations dont want 20 fnew values when n=20 there any, , mean any, way around this? appreciated!

sounds want for loop go 40 small piece of codes runs i=20? have if statement lets parts of codes evaluated when i <= 20. following?

for = 1:n     disp(['iteration count =' num2str(i)])     if (i <= 20)         x = p + (i * h);         fadd = f(x);         fnew = fold + fadd;         disp(['fnew = ' num2str(fnew)])         fold = fnew;     end end