Hi I have a rather simple question. Can anybody please tell me how can I extract the upper triangle portion of a matrix without its diagonal elements in a vector?
if a = { 1 2 3, 4 5 6, 7 8 9} is a matrix I want to extract 2,3,6 in this order, is there a quick way to do that without using loop?
Thanks
Annesha
2 Answers
0
I am not sure this is the absolute best method, but it is certainly better than a for loop:
One line solution
a_uv = packr(vech(diagrv(x, error(0))'));
Verbose 'proc' with explanation of steps
a = { 1 2 3,
4 5 6,
7 8 9 };
a_uv = upmatND(a);
proc (1) = upmatND(x);
//replace diagonal with missing values
//error(0) is equivalent to a missing
x = diagrv(x, error(0));
//Remove the lower triangle of
//transposed matrix and return
//as a vector
x = vech(x');
//Remove diagonal elements
//which we set to missing values
//above
x = packr(x);
retp(x);
endp;
Your Answer
2 Answers
0
I am not sure this is the absolute best method, but it is certainly better than a for loop:
One line solution
a_uv = packr(vech(diagrv(x, error(0))'));
Verbose 'proc' with explanation of steps
a = { 1 2 3,
4 5 6,
7 8 9 };
a_uv = upmatND(a);
proc (1) = upmatND(x);
//replace diagonal with missing values
//error(0) is equivalent to a missing
x = diagrv(x, error(0));
//Remove the lower triangle of
//transposed matrix and return
//as a vector
x = vech(x');
//Remove diagonal elements
//which we set to missing values
//above
x = packr(x);
retp(x);
endp;