Find repeated row from col1, average repeated from col2, erase repeated row

Hi, I have matrix A (7x2) where the first column has some repeated rows

A=[54.5 300; 56 250; 57 100; 56 600; 56.5 700; 57 800; 58 900]

In A, the number 56 repeats two times, the number 57 also repeats two times. [a number can be repeated a max of two times]

Whenever the number from the 1st column repeats, I need to take the average from the second column [so for 56 would be (250+600)*0.5=425] and re-express the matrix with that average in col2, and erase the repeated rows.

So the resulting matrix B would be 5x2 like this:

B= [54.5 300; 56 425; 56.5 700; 57 450; 58 900]

Any ideas please? I tried with ismember but cannot work with 0 indices. Thanks Dave

Answer 1

[the cyclist]

[B1,~,j] = unique(A(:,1));

B2 = accumarray(j,A(:,2),[],@mean);

B = [B1,B2]