I am trying to build this code to where I can type either YES or NO when asked for the input in line 1, but whenever I type NO, an error pops up saying "Matrix dimensions must agree". I am not sure where I am going wrong.

 tail_stinger = input('Has a tail/stinger?','s');
if tail_stinger == 'YES'
    straight_tail = input('Tail straight like a needle?','s');
    if straight_tail == 'YES'
        disp('Order Uropygi')
    else straight_tail = 'NO';
        disp('Order Scorpiones')
    end
else tail_stinger = 'NO';
    claws = input('Has claws?','s');
    if claws == YES
        length_flat = input('Less than 5mm long or flat?','s');
        if length_flat == YES
            disp('Order Pseudoscorpiones')
        else 
            disp('Order Amblypygi')
        end
    end
end

Answer 1

[JESUS DAVID ARIZA ROYETH]

for compare two strings use strcmp :

if strcmp(tail_stinger,'YES')