Problem with find and logical array

Question

Urvashi 2014-6-6

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编辑： Urvashi 2014-6-6

Hi,

I have a matrix with the values : A = [260,343; 344,433; 434,530; 531,631; 632,723];

where A(:,1) is the lower range and A(:,2) = upper range for each row. I am trying to find the index of A where a number may exist within the upper and lower range.

For ex. I tried B = (443 > A(:,1) & A(:,2) > 443) to check in which row the number 443 would lie, but got the ans as 0, even though when B comes as = [0,0,1,0,0]. I performed index = find(B),

I am probably doing something stupid. What am I doing wrong?

Thanks, Urvashi

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Urvashi 2014-6-6

I know. I will download 'find' again. May be it's a problem with my function

Geoff Hayes 2014-6-6

What do you mean by "download 'find' again"? Are you using a different version of find from the built-in one?

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Answer 1

Sara 2014-6-6

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编辑：Sara 2014-6-6

在 MATLAB Online 中打开

You could do:

B = find(443 > A(:,1) & A(:,2) > 443);

B is the row or rows where the condition is satisfied.

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Urvashi 2014-6-6

I did that too, and still got the answer as B = 0. There might be something wrong with the function 'find' in my version. I should probably download it again.

Sara 2014-6-6

Yeah, could be, because everybody here is getting the right result.

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Answer 2

Image Analyst 2014-6-6

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https://ww2.mathworks.cn/matlabcentral/answers/132731-problem-with-find-and-logical-array#answer_139670

在 MATLAB Online 中打开

I don't see any problem:

A = [260,343; 344,433; 434,530; 531,631; 632,723]
targetValue = 443
logicalRowsInRange = (targetValue > A(:,1) & A(:,2) > targetValue) 
rowInRange = find(logicalRowsInRange)
A =
   260   343
   344   433
   434   530
   531   631
   632   723
targetValue =
   443
logicalRowsInRange =
     0
     0
     1
     0
     0
rowInRange =
     3

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Answer 3

Urvashi 2014-6-6

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https://ww2.mathworks.cn/matlabcentral/answers/132731-problem-with-find-and-logical-array#answer_139672

编辑：Urvashi 2014-6-6

Yeah, thanks a lot. It worked. I had missed a ) in one of my previous statements of find, so find ended up being an empty matrix. And I didn't realize that the variable find was generated as there was a huge list of variables being generated during the program run.

My bad. Really, my bad.