create a matrix without using loop or nested loop operations in MATLAB

Question

I want to create a matrix without using any loop, like in the following program I made in MATLAB 2011a for forming matrix n(x,y).

segment1 and segment2 have the same dimensions (you can take any two matrices).

segment1 = [1 2 3;4 5 6];
segment2 = [5 2 6;9 1 2];

seg1_max = max(max(segment1));
seg2_max = max(max(segment2));

n = zeros(seg1_max, seg2_max);
i = 1; j = 1;

while i<=size(segment1, 1)        
    while j<=size(segment1, 2)    
        x = segment1(i, j);
        y = segment2(i, j);
        n(x,y) = n(x,y)+1;
        j = j+1;    
    end;
i = i+1; j = 1;
end;

I have also made this program using for loop, but i want to get matrix n(x,y) without using loop operations.

Warren Weckesser · Accepted Answer · 2012-09-08 03:27:57Z

2

The function accumarray can be used for this. Given your segment1 and segment2, the following computes m, which will be the same as your n:

x = segment1(:);
y = segment2(:);
m = accumarray([x y], ones(size(x)));

answered Sep 8, 2012 at 3:27

Warren Weckesser

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