max function does not work

      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