How to extract specific entries from a matrix?

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Scott Dallas
Scott Dallas 2015-7-1
评论： Brendan Hamm 2015-7-1
Hi there,
I have a 100,001x7 matrix. I want to obtain the exact location of each entry in column 2 that equals a specific number. For example I want to know which rows in column 2 have an entry equal to 5.
Is there a way to do this on Matlab?
Any help is much appreciated, Scott.

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回答（1 个）

Andrei Bobrov
Andrei Bobrov 2015-7-1
A = randi(2000,100001,7); % let this is your data
out = find(A(:,2) == 5);
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Andrei Bobrov
Andrei Bobrov 2015-7-1
Like this is:
intr = [4.5,5.5];
out = find(intr(1) <= A(:,2) & intr(2) >= A(:,2));
Brendan Hamm
Brendan Hamm 2015-7-1
Or you could do something like:
tol = 0.5; % tolerance
idx = abs(A(:,2) - 5) < tol; % logical vector of locations within tolerance
Now the actual values can be extracted with:
A(idx,2)
or the entire row with
A(idx,:)

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