[Numpy-discussion] degree matrix construction

Satya Upadhya satyaupadhya at yahoo.co.in
Fri Sep 15 08:09:25 CDT 2006

Dear Friends,
my question is the following:

Suppose i have the following code:

>>> from LinearAlgebra import *

>>> from Numeric import *
>>> A = [1,2,1,3,1,3,4,1,2]
>>> B = reshape(A,(3,3))
>>> C = sum(B,1)
>>> C
array([4, 7, 7])

Now, my problem is to construct a degree matrix D which is a 3 * 3 matrix with diagonal elements 4,7,7 (obtained from the elements of C) and all off-diagonal elements equal to 0.
Could some kind soul kindly tell me how to do this.
I've looked at the help for the diagonal function and i am unable to do what i wish to. Furthermore i dont understand the meaning of axis1 and axis2:
>>> help (diagonal)
Help on function diagonal in module Numeric:

diagonal(a, offset=0, axis1=0, axis2=1)
    diagonal(a, offset=0, axis1=0, axis2=1) returns all offset diagonals
    defined by the given dimensions of the array.


Thanking you,

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