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issues with function find()

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Camille
Camille 2013-3-2
I am using find() to find the index of a number in a matrix, but it is returning an empty matrix yet am sure that the number is part of that matrix. Here is the code
tr=0:.1:20;
b=find(tr==2.4)
and it is returning
b =
Empty matrix: 1-by-0
Please I need your help. What am I doing wrong or what should I do instead?

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采纳的回答

Azzi Abdelmalek
Azzi Abdelmalek 2013-3-2
Try this
tr=0:.1:20;
b=find(tr==0.1*24)

更多回答（1 个）

Brian B
Brian B 2013-3-2
编辑：Brian B 2013-3-2
Try
tr=0:.1:20;
tr = round(tr*1e12)/1e12;
b=find(tr==2.4)
This is a problem with finite precision. See the explanation offered at http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F.
  1 个评论
Brian B
Brian B 2013-3-2
Actually, if you're using non-integer numbers, a better method is
b= find(abs(tr - 2.4)<1e-12)

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