How can I re-arrange a matrix?

Hi everyone,

Let's assume that I have a matrix X, dimensions 10x2, a variable z of dimensions 10x1. Then I want to create an interaction term based on the sorted values of y, so that the first half gets 0 and the highest values get 1. Then I want to regress the interaction term on variable y.

x = randn(10,2);
z = randn(10,1);
y = randn(10,1);
[zsorted,zsindex]=sort(z);
zsorted(1:5)=0; zsorted(6:end)=1; 
% Interaction Term
intterm = x(zsindex,:).*zsorted;

How can i transform the elements of the interaction term back to the original order of x? I could get the same results by

res  = ols(y(zsindex,:), intterm);

But is there any other way to be done?

Thanks in advance.

Answer 1

[Walter Roberson]

z = randn(10,1);

[~,zsindex]=sort(z);
intterm = z;
intterm(zsindex(1:end/2)) = 0;

[gsourop]

Many thanks!