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expm doesn't work correctly.
From: |
che6yoh |
Subject: |
expm doesn't work correctly. |
Date: |
Tue, 25 May 93 17:37:25 BST |
Dear Sirs,
I am using octave-0.71.1 installed with gcc-2.3.3 on sun
SPARC(sunOS-4.1.1).
expm doesn't work correctly.
I add two examples of expm strange results.
For simple matrix like a=[1,2;3,4],
the correct answer is given by expm(a);
The trouble seems to be occured when the Jordan form of the
matrix is not diagnal.
Is the trouble caused by my installation or a bug of octave?
I am looking forward to getting reply.
I am sorry I sent a mail without my name or address.
Yoshihiro Hashimoto
Dept. of Systems Eng., Nagoya Inst. of Tech.
address@hidden
[Now]Dept. of Chem. Eng., The Univ. of Leeds
address@hidden
--------------------------------------------------------------
The mail to address@hidden will be sent to
address@hidden automatically.
===============================================================
[EXAMPLE1]
octave:1> f=[0 1 0 0 0;0 0 1 0 0;0 0 0 0 0;0 0 0 0 0;0 0 0 0 0]
f =
0 1 0 0 0
0 0 1 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
octave:2> g=expm(f)
g =
1 -1 1 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 1 0
0 0 0 0 1
The result of MATLAB is
MATLAB>> g=expm(f)
g =
1.0000 1.0000 0.5000 0 0
0 1.0000 1.0000 0 0
0 0 1.0000 0 0
0 0 0 1.0000 0
0 0 0 0 1.0000
[EXAMPLE2]
octave:4> w=[0 0 0 0 0.3;0.3 -0.42 -0.42 -0.3 0;0 0.3 0 0 0;0 0
0.3 0 0;0 0 0 0
0]
w =
0 0 0 0 0.3
0.3 -0.42 -0.42 -0.3 0
0 0.3 0 0 0
0 0 0.3 0 0
0 0 0 0 0
octave:5> v=expm(w)
v =
(0.408248, 0) (0.408248, 0) (0.408248, 0) (0.5, 0) (-0.5, 0)
(2.84938e-16, -0.402859) (-0.00663493, 0.00348261) (0.545972, 0.286576)
(0.302438, -2.87586e-16) (-0.302438, 2.56773e-16)
(-2.74237e-16, 0.552394) (0.545972, -0.286576) (-0.211754, -0.111148)
(-0.302438, 3.94334e-16) (0.302438, -3.52084e-16)
(0.408248, 0.181901) (0.196494, 0.111148)
(-0.0530224,-0.242117) (0.802438, 1229853e-16) (-0.802438, -1.1594e-16)
(0, 0) (0, 0) (0, 0) (0, 0) (0, 0)
v must be a real matrix.
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