[Tutor] cannonical matrix representation?
What's the best way to represent a matrix M with 4 dimensions, such as M[x][y][z][t] where each element in the sparse matrix could be a simple number, or could be an executable Python function snipped that returns a value when that cell is evaluated? The user of the program will type in Python functions to be inserted into particular cells in the 4-D matrix. I did't see any package that exactly does this; do I write my own Matrix class and base it on lists? Thanks! -Mike p.s. This seems to me like it ought to be built into the base language - multidimensional object arrays. (Indeed, maybe it is, and I'm just too dense to notice!) ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] cannonical matrix representation?
On 2/10/06, Mike Cheponis [EMAIL PROTECTED] wrote:
What's the best way to represent a matrix M with 4 dimensions, such as
M[x][y][z][t] where each element in the sparse matrix could be a simple
number, or could be an executable Python function snipped that returns a
value when that cell is evaluated?
The user of the program will type in Python functions to be inserted into
particular cells in the 4-D matrix.
I did't see any package that exactly does this; do I write my own Matrix
class and base it on lists?
Thanks! -Mike
If it is a truly sparse matrix, I would use a dictionary with tuples
as keys; i.e.,
m{(x, y, z, t) = element}
André
p.s. This seems to me like it ought to be built into the base language -
multidimensional object arrays. (Indeed, maybe it is, and I'm just too dense
to notice!)
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Re: [Tutor] cannonical matrix representation?
p.s. This seems to me like it ought to be built into the base language - multidimensional object arrays. The only languages I know that truly support anything like what you want are programmes like Mathematica and arguably MS Excel Basic... There is a pseudo mathematica somewhere in Python but otherwise its roll your own time ... I think... Which usually means its time for somebody to find a ready wrapped solution :-) Alan G Author of the learn to program web tutor http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] cannonical matrix representation?
| 3. cannonical matrix representation? (Mike Cheponis)
|
| What's the best way to represent a matrix M with 4 dimensions, such
| as M[x][y][z][t] where each element in the sparse matrix could be a
| simple number, or could be an executable Python function snipped that
| returns a value when that cell is evaluated?
|
| The user of the program will type in Python functions to be inserted
| into particular cells in the 4-D matrix.
|
| I did't see any package that exactly does this; do I write my own
| Matrix class and base it on lists?
I don't know how full-blown of a solution that you need, but a little helper
function for dictionaries (as was noted as a good way to deal with a sparse
pmatric) might suffice, something like this,maybe.
###
def setdict(d,v,*k):
#args = dictionary, value, key all separated by commas
d[tuple(k)]=str(v)
def evaldict(d,*k):
#return the evaluated entry at key k in dictionary d
return eval(d[tuple(k)])
d={}
setdict(d,1,1,2)
setdict(d,'x+3',2)
print d
x=3
print evaldict(d,1,2)
print evaldict(d,2)
### output
{(1, 2): '1', (2,): 'x+3'}
1
6
###
The evaluation will pull its values from the context in which the evaldict is
being made. There are ways to get around this, but just ask if you need/want to
go this direction.
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