How to extract specific entries from a matrix?

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.

Answer 1

[Andrei Bobrov]

A = randi(2000,100001,7); % let this is your data

out = find(A(:,2) == 5);

[Scott Dallas]

Thanks for your answer.

I used the code and it worked but I now realize that what I really need are entries that are close to but not necessarily equal to the specific number. For example say the number is 5, I want to find all entries within a particular range of 5.

Is there a way to do this?

Best Wishes, Scott.

[Andrei Bobrov]

Like this is:

intr = [4.5,5.5];
out = find(intr(1) <= A(:,2) & intr(2) >= A(:,2));

[Brendan Hamm]

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,:)