# How to a find the frequency of a point or values?

9 views (last 30 days)
John Alperto on 6 Apr 2015
Answered: Star Strider on 6 Apr 2015
If I have a Nx2 vector (in this case, N=20): A =
0 1
0 1
1 0
0 -1
0 -1
-1 0
-1 0
0 1
0 1
1 0
0 -1
0 -1
-1 0
-1 0
0 1
-1 0
1 0
0 -1
0 -1
-1 0
I want to know how many times each unique point (-1,0), (1,0), (0,1), and (0, -1) appears in this vector. For example, the point (-1,0) occurs 6 times. Is there a fast, simple way to do this? Using the find function or a for loop were too cumbersome I thought, but I couldn't find a simple function that would help with this. Is anyone aware of a function, or a simple method to accomplish this? Thanks

Mahdiyar on 6 Apr 2015
Hi
you can download the matlab function named findsubmat from the following link. Then use it for each pair. For example:
B1 = findsubmat(A, [-1 0]);
B2 = findsubmat(A, [1 0]);
B3 = findsubmat(A, [0 1]);
B4 = findsubmat(A, [0 -1]);
Regards,
John Alperto on 6 Apr 2015
Thanks.

Star Strider on 6 Apr 2015
This works:
A = [0 1
0 1
1 0
0 -1
0 -1
-1 0
-1 0
0 1
0 1
1 0
0 -1
0 -1
-1 0
-1 0
0 1
-1 0
1 0
0 -1
0 -1
-1 0];
[Au,~,ic] = unique(A,'rows');
k = accumarray(ic,1);
fprintf('\n\tPoints\tFrequency\n')
fprintf('\t%2d %2d\t\t%2d\n', [Au k]')
and produces:
Points Frequency
-1 0 6
0 -1 6
0 1 5
1 0 3

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