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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