max function does not work with zero

Hello I am trying to use the max function, but it will not work. I have attached my log file. I have tried using this function maxStcev=max(Stcev'-K,0); (line 52), but I keep getting negative values.

I have then tried using a for loop with if statement, but this results in error: "Index exceeds matrix dimensions.

Error in mccev (line 45) if (M1(1,o)<0)" Can someone see what I am doing wrong? I want t have a vector only with positive values. Regards, Søren