MATLAB Answers

How to use not equal to '~=' operator in if statement?

1.769 views (last 30 days)
Show older comments
Sohail Ahmed
Sohail Ahmed on 21 Feb 2017
  • 1
Commented: Walter Roberson on 28 Nov 2017
My code works fine with '==' but not with '~='.I expect it not to display 'error' if user enters A or B
x=input('input x','s')
if(x~='A')||(x~='B')
disp('error');
end

Sign in to answer this question.

Accepted Answer

John D'Errico
John D'Errico on 21 Feb 2017
Edited:John D'Errico on 21 Feb 2017
A problem of elementary logic?
You want an error to return only if A is not in the set {'A','B'}. So a call to ismember might be a good alternative.
Regardless, given the approach you have followed, if x is equal to 'A', then the second half of the clause will be true, even though the first part of the clause is false. And the logical statement
假| | true
is TRUE.
You are asking for a result that is only true when BOTH parts of the clause are true. Use a logical and, NOT a logical or.
if(x~='A') && (x~='B')

More Answers (2)

Jan
Jan on 21 Feb 2017
Remember, that the negation of
(x=='A') || (x=='B')
is:
~((x =='A') || (x =='B')) ==>
~(x =='A') && ~(x =='B') ==>
(x ~='A') && (x ~='B')
2 Comments
Show 1 older comment
Walter Roberson
Walter Roberson on 28 Nov 2017
ifany((x ~='a') & (x ~='p') & (x ~='T'))
fprintf('ERROR:You entered incorrect choice.')
end
or
if~all( ismember(x, {'a','p','T'}) )
fprintf('ERROR:You entered incorrect choice.')
end

Sign in to comment.

Torsten
Torsten on 21 Feb 2017
Edited:Torsten on 21 Feb 2017
If user enters A, then x~=B is true, so (x~='A')||(x~='B') is true, thus "error" is displayed.
Same for B.
Best wishes
Torsten.

Categories

Tags

下载188bet金宝搏

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by