svec2

 [evec, idiag] = svec2(emat)
 vectorization of a (generally full) symmetric matrix; 
 upper triangle is vectorized row-wise
 INPUT: evac...symmetric matrix
 OUPUT: evec...upper triangle of emat stored row-wise in a vector
        idiag...vector oex72f indices of diagonal entries of emat in evec

0001 function [evec, idiag] = svec2(emat)
0002 %
0003 % [evec, idiag] = svec2(emat)
0004 % vectorization of a (generally full) symmetric matrix;
0005 % upper triangle is vectorized row-wise
0006 % INPUT: evac...symmetric matrix
0007 % OUPUT: evec...upper triangle of emat stored row-wise in a vector
0008 %        idiag...vector oex72f indices of diagonal entries of emat in evec
0009 
0010 % This file is a part of PENLAB package distributed under GPLv3 license
0011 % Copyright (c) 2013 by  J. Fiala, M. Kocvara, M. Stingl
0012 % Last Modified: 27 Nov 2013
0013 
0014 m = size(emat,2);
0015 idiag(1) = 1;
0016 k = m;
0017 
0018 evec = zeros(m*(m+1)/2,1);
0019 evec(1:m) = emat(1:m,1);
0020 for j=2:m
0021     i = idiag(j-1) + k;
0022     idiag(j) = i;
0023     k = k-1;
0024     evec(i:i+k-1) = emat(j:m,j);
0025 end
0026 
0027 end