Error using == Matrix dimensions must agree

Question

my system will give me the a/m error when I input more than 3 characters

a = input('Please type f0 or f1: ' , 's');

if a == 'f0'; 
    Run_f0
elseif a == 'f1';
    Run_f1 
else 
    disp('Please enter f0 or f1 only');
end

what should I do to resolve this error? Thanks in advance

Nras Nras · Accepted Answer · 2014-09-22T07:15:09

Matlab will compare each character of both strings. If one string is longer than the other one, there is nothing to compare and it will throw an error. You can bypass this by forcing the user to repeat the input until he gives a valid input:

valid = {'f0', 'f1'}
a = input('Please type f0 or f1: ' , 's');
while not(ismember(a, valid))  %// or: while not(any(strcmp(a, valid)))
    a = input('Please really type f0 or f1: ' , 's');
end

The user will be asked to really input 'f0' or 'f1'.

As an alternative, you can consider to compare the strings with strcmp():

if strcmp(a, 'f0')
    %// something
elseif strmpc(a, 'f1')
    %// something else
else
    disp('Please enter f0 or f1 only');
end

Error using == Matrix dimensions must agree

2 Answers