AMBER Archive (2008)Subject: AMBER: Problem of Ptraj analyze matrix
From: Qi Yan (kid1412_at_uab.edu)
Date: Mon Jun 09 2008  08:37:01 CDT
Hi,all:
When calculating the first eigenvector, I found a problem. I used two
different ptraj.in files and got an opposite result of eigenvector.
first ptraj1.in (I just calculated the first eigenvector):
rms first @CA
matrix covar name cvmat @CA out cvmat.dat
analyze matrix cvmat out eigen_covar.dat vecs 1
first result:
1 6682.90154
0.02344 0.00701 0.00270 0.00799 0.00716 0.00631
0.00676
0.01184 0.01257 0.00844 0.01400 0.01116 0.00726
0.01468
... ...
second ptraj2.in (the difference is that I calculate the first two
eigenvectors, but the very first eigenvector is what I want):
rms first @CA
matrix covar name cvmat @CA out cvmat.dat
analyze matrix cvmat out eigen_covar.dat vecs 2
second result:
1 6682.90154
0.02344 0.00701 0.00270 0.00799 0.00716 0.00631
0.00676
0.01184 0.01257 0.00844 0.01400 0.01116 0.00726
0.01468
... ...
We can see the sign of values is opposite. I have no idea why this
happened? Does anybody point me out?
Thanks in advance,
Qi

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