Hi, Vincent,
Yes, my matrix is sparse. I just move here from matlab, so I am a
newbie for sage and python.
The function you have offered can do the job. But I am worried about its
efficiency, because my sparse matrix
maybe very large which comes from Finite Element method.
So about the efficient ways for sparse matrix, can you give me some
suggestion? Thanks very much.
Best
Huayi
On 2015年05月20日 14:26, Vincent Delecroix wrote:
Hi Huayi,
On 20/05/15 08:20, Huayi Wei wrote:
I have a sage matrix, and I want to get its left-lower and right-upper
triangular parts. Does there exist any method to get them directly?
In matlab, there are two functions `triu` and `tril` to do such things.
Does sage have the similar functions?
It does not seem to exists. Sage only has a `diagonal` method to
return the list of entries on the diagonal.
Do you know how to implement it in Sage? Otherwise the small function
below does the job
def triu(m):
t = matrix(m.base_ring(), m.nrows())
for i in range(m.nrows()):
t[i,i:] = m[i,i:]
return t
Though, if your matrices are sparse, there are more efficient ways for
sure.
Best,
Vincent
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