why do I get the error: Undefined function or variable 'a'.?

clear
clc

for m=6:3
    a(m)=m^2
    b(m)=m*s
end
a
b

Answer 1

[Star Strider]

The problem is the way you index your for loop:

for m=6:3

The colon (link) operator default behaviour is to increment by 1 from the first value to the last. Here, the last value is lower than the first, so the loop limit is already satisfied at the start, and the loop does not execute and so does not calculate ‘a’ (or ‘b’). To modify that behaviour, set the increment to -1:

for m=6:-1:3
    a(m)=m^2
    b(m)=m*s
end

The loop now executes, although since ‘s’ is not defined here, will crash on the ‘b’ assignment line.

Answer 2

[Steven Lord]

You're using the valArray syntax for the for keyword. That section of the documentation states the maximum number of times the loop will execute. Based on the information in that section of the documentation, what is that maximum number of loop executions for your example?