why do I have unrecognized function error for z?

I thought I defined z by putting it in the switch.

[KSSV]

Don't attach your code as a image snippet. You can always copy paste your code here.

What is variable buff?

Answer 1

[Steven Lord]

What should the value of z be if buff is none of "none", "30min", or "60min"? What if buff was "30 minutes", for example?

Answer 2

[VBBV]

%if true
buff = char(buff);% convert to char or number 
 switch buff
     case 'none'
         z = 0;
     case '30min'
         z = 12;
     case '60min'
         z = 24;
  end

If the input value contains only numeric, then conversion to char is not necessary. e.g. case 0, case 30 case 60. Otherwise it's needed in switch as shown abov In your program, the switch case is not being executed and directly jumps to next line after end.