Repeated Values in matrix

Dear All;

I have an array of two columns, I want to find each repeated values of y for each x value and then the max of these y value to this x value and make new matrix in which for each x value there is a unique y value

how to do that ?

[Walter Roberson]

What do you want done if one of the y values is unique instead of being repeated?

Answer 1

[Walter Roberson]

[uvals, ua, uc] = unique(xy(:,1));
maxy = accumarray(uc(:), xy(:,2), [], @max);
newarray = [uvals(:), maxy(:)];

Answer 2

[Azzi Abdelmalek]

v=[1 2;1 3;4 5;4 20;10 30]
[ii,jj,kk]=unique(v(:,1))
out=[ii accumarray(kk,v(:,2),[],@max)]