[Numpy-discussion] Regarding Matrices

Nils Wagner nwagner at iam.uni-stuttgart.de
Mon Aug 14 15:24:20 CDT 2006


On Mon, 14 Aug 2006 21:58:50 +0200
  Sven Schreiber <svetosch at gmx.net> wrote:
> Hi,
> 
> Satya Upadhya schrieb:
> 
>>>>> from Numeric import *
> 
> Well this list is about the numpy package, but anyway...
> 
>> the power function is giving a resultant matrix in which 
>>each element of
>> matrix B is raised to the power of 0 so as to make it 1. 
>>But, taken as a
>> whole i.e. matrix B to the power of 0 should have given 
>>the identity
>> matrix.
> 
> afaik, in numpy terms if you are dealing with a numpy 
>array, such
> functions are elementwise by design.
> In contrast, if you have a numpy matrix (a special 
>subclass of the array
> class) --constructed e.g. as mat(eye(3))-- then power is 
>redefined to be
> the matrix power; at least that's the rule for the ** 
>operator, not 100%
> sure if for the explicit power() function as well, but I 
>suppose so.
> 
>>  
>> Also, what is the procedure for taking the log of an 
>>entire matrix
>> (log(A) where A is a matrix takes the log of every 
>>individual element in
>> A, but thats not the same as taking the log of the 
>>entire matrix)
> 
> I don't understand what you want, how do you take the 
>log of a matrix
> mathematically?
> 
> -Sven
> 
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Help on function logm in module scipy.linalg.matfuncs:

logm(A, disp=1)
     Matrix logarithm, inverse of expm.

Nils




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