Member Avatar for XodoX

I'm new to Python, but I can use a library to do this, right? Like this one:

import pprint
import scipy
import scipy.linalg   # SciPy Linear Algebra Library

A = scipy.array([ [7, 3, -1, 2], [3, 8, 1, -4], [-1, 1, 4, -1], [2, -4, -1, 6] ])
P, L, U = scipy.linalg.lu(A)

print "A:"
pprint.pprint(A)

print "P:"
pprint.pprint(P)

print "L:"
pprint.pprint(L)

print "U:"
pprint.pprint(U)

First of all, is this an ok way of doing it? And, how about pivoting ? Is there something that can do this for me or do I have to come up with a seperate algorithm ?

P.S. I just noticed that it dosen't even compile :( Or, I'm not doing it right. But this compiler should work.

"SyntaxError: multiple statements found while compiling a single statement".

Edited by XodoX
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  • Latest Post Latest Post by Gribouillis
Member Avatar for Gribouillis

It works for me and python 2.7. The output is

A:
array([[ 7,  3, -1,  2],
       [ 3,  8,  1, -4],
       [-1,  1,  4, -1],
       [ 2, -4, -1,  6]])
P:
array([[ 1.,  0.,  0.,  0.],
       [ 0.,  1.,  0.,  0.],
       [ 0.,  0.,  1.,  0.],
       [ 0.,  0.,  0.,  1.]])
L:
array([[ 1.        ,  0.        ,  0.        ,  0.        ],
       [ 0.42857143,  1.        ,  0.        ,  0.        ],
       [-0.14285714,  0.21276596,  1.        ,  0.        ],
       [ 0.28571429, -0.72340426,  0.08982036,  1.        ]])
U:
array([[ 7.        ,  3.        , -1.        ,  2.        ],
       [ 0.        ,  6.71428571,  1.42857143, -4.85714286],
       [ 0.        ,  0.        ,  3.55319149,  0.31914894],
       [ 0.        ,  0.        ,  0.        ,  1.88622754]])

I don't understand your question about pivoting. Do you mean using permute_l = True in the call to lu() ?

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