Find function for Matrix

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Jonathan Moorman 2020-8-20

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评论： Jonathan Moorman 2020-8-20

Hi! I'm trying to use the find function for the first time in my code and have come across a problem. It appears that in about half my runs, the function is unable to find the value in the matrix when it is clearly there. Has anyone seen this error before or am I doing something incorrect in the code?

Below is three screenshots of the value it should be looking for (0.1573), in the matrix (a90Export6dB), and I am getting a empty vector when the value is clearly there.

Figure 1:

Figure 2:

Figure 3:

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Answer 1

KSSV 2020-8-20

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编辑：KSSV 2020-8-20

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When you are comapring a floating point number you should not use ==, you should fix some tolerance and use inqualitty. Check the below example code:

tol = 10^-5 ; 
val = rand ; 
A = rand(1,10) ;
A(5) = val ;   % replace this index with vl to seek later 
idx = abs(A-val)<=tol ; % logical indices 
id = find(idx) % index 