[sage-support] Entering matrices whose elements are functions of row/column indices?

2010-03-13 Thread Alasdair
This can be done in maxima:

genmatrix(lambda([i,j],i-j),6,6);

for example.  But is there an easy Sage way of doing this?  If I enter

sage: M=maxima('genmatrix(lambda([i,j],i-j),6,6)')

then I obtain a Maxima matrix, which then has to turned into a Sage
matrix (I don't know how to do this either).  Clearly I could:

sage: M=matrix(ZZ,6,6)
sage: for i in range(6):
: for j in range(6):
: M[i,j]=i-j

but that seems a bit longwinded.  Is there an easy straightforward
way?

Thanks,
Alasdair

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Re: [sage-support] Entering matrices whose elements are functions of row/column indices?

2010-03-13 Thread David Joyner
Here is another way:

sage: coeffs = [[i^2-j for j in range(6)] for i in range(6)]
sage: matrix(coeffs)
[ 0 -1 -2 -3 -4 -5]
[ 1  0 -1 -2 -3 -4]
[ 4  3  2  1  0 -1]
[ 9  8  7  6  5  4]
[16 15 14 13 12 11]
[25 24 23 22 21 20]


On Sat, Mar 13, 2010 at 7:58 AM, Alasdair amc...@gmail.com wrote:
 This can be done in maxima:

 genmatrix(lambda([i,j],i-j),6,6);

 for example.  But is there an easy Sage way of doing this?  If I enter

 sage: M=maxima('genmatrix(lambda([i,j],i-j),6,6)')

 then I obtain a Maxima matrix, which then has to turned into a Sage
 matrix (I don't know how to do this either).  Clearly I could:

 sage: M=matrix(ZZ,6,6)
 sage: for i in range(6):
 :     for j in range(6):
 :         M[i,j]=i-j

 but that seems a bit longwinded.  Is there an easy straightforward
 way?

 Thanks,
 Alasdair

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