Using AND Operator in “if” statements
조회 수: 978 (최근 30일)
이전 댓글 표시
Hi, When I type the following code: if size([1 2 3])==size([4 5 6]) & size([4 5 6])==size([7 8 9]) 'yes' else 'no' end MATLAB Code Analyzer issues this warning message: "When both arguments are numeric scalars, consider replacing & with && for performance." So, I use && instead of &: if size([1 2 3])==size([4 5 6]) && size([4 5 6])==size([7 8 9]) 'yes' else 'no' end But when I run the updated script, MATLAB displays an error message in the Command Window: ??? Operands to the || and && operators must be convertible to logical scalar values. What can I do to fix this? Thanks in advance. Andrew DeYoung Carnegie Mellon University
댓글 수: 7
Matt Tearle
2011년 5월 11일
You're right about IF and vectors, but the Code Analyzer doesn't necessarily know which variables are vectors and which aren't. The & operator is one instance where it can give a message without having to determine that. The str2num vs str2double message is another example. It's vaguely annoying to get a warning, but the Analyzer's just hedging its bets.
[BTW, I'm just passing on the "official" answer here. I was about to submit a request saying, basically, exactly what you've said. But I found an existing discussion, and I've paraphrased the end decision. I'm sure there's more to it than I can skim and pass along.]
Jenny
2016년 8월 2일
Matt, I still use my notes from your class, and thanks for the help in this question. I needed to get this right.
채택된 답변
Andrew Newell
2024년 11월 21일
편집: MathWorks Support Team
2024년 11월 21일
The problem is that size returns a vector: size([1 2 3]) ans = 1 3 Instead, use |numel|: if numel([1 2 3])==numel([4 5 6]) && numel([4 5 6])==numel([7 8 9]) disp('yes') else disp('no') end Or you could use |all(size([1 2 3])==size([4 5 6])| etc. I have also put in the |disp| commands to take care of the other warnings.
추가 답변 (1개)
Sean de Wolski
2011년 5월 10일
As an addendum to Andrew's thorough and good solution, you can check the sizes directly:
if(isequal(size([1 2 3]),size([4 5 6])))
disp('yes')
else
disp('no')
end
This will fail if the sizes are not the same but the number of elements (numel) is:
if(isequal(size([1 2 3]),size([4; 5; 6])))
disp('yes')
else
disp('no')
end
댓글 수: 3
Matt Tearle
2011년 5월 10일
Another benefit to isequal is that it won't throw an error message in situations where == will (it will just return false). For example
if size(rand(2))==size(rand(3,2,2))
disp('yes')
else
disp('no')
end
will fail because size will return a 3-element vector for a 3-D array. However
if isequal(size(rand(2)),size(rand(3,2,2)))
disp('yes')
else
disp('no')
end
works fine.
참고 항목
카테고리
Help Center 및 File Exchange에서 Loops and Conditional Statements에 대해 자세히 알아보기
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!