Array indices must be positive integers or logical values. Error in untitled4 (line 9) max(num)=0;

syms a b x
num=input('Your student number is:');
m=max(num);
max(num)=0;
n=0;

Answer 1

[Walter Roberson]

The syms is unused by the remainder of the code.

You are not validating that the user is entering a scalar positive integer.

You are taking max() of a scalar integer, which is going to return the number itself.

Unless, that is, you are expecting that the user is going to enter a vector of digits?? If so then one of the digits could be 0, and using 0 as an index into the new variable max you are creating would be an error.

Have you considered looking at the second output of max() ?

And we strongly recommend against using either max or sum as the names of variables: it rarely ends well for anyone.