#13564: Improve diagonal from matrix/matrix2.pyx
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Reporter: r.gaia.cs | Owner: jason, was
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-5.5
Component: linear algebra | Resolution:
Keywords: matrix, diagonal | Work issues:
Report Upstream: N/A | Reviewers:
Authors: r.gaia.cs | Merged in:
Dependencies: | Stopgaps:
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Comment (by ppurka):
Some comments:
1. Should we be raising an error or simply returning an empty list if the
`d` for the `d`-th diagonal is provided outside the range of the number of
rows or columns? For instance, the empty matrix is returning an empty
diagonal. Also,
[http://www.wolframalpha.com/input/?i=Diagonal%5B%7B%7B1%2C+2%2C+3%2C+4%7D%2C+%7B5%2C+6%2C+7%2C+8%7D%2C+%7B9%2C+10%2C+11%2C+12%7D%7D%2C+4%5D
Mathematica] and Matlab silently return empty matrices. Octave raises an
error. Numpy gives an empty matrix until `nrows()` or `ncols()` and then
raises an error.
2. If it seems more proper to raise an error, the error string could be
written like the statements below. Note that `d` is always ''less than''
and never equal to `nrows()` or `ncols()`.
{{{
The value `d` should be less than the number of columns in the matrix.
The value `-d` should be less than the number of rows of the matrix.
}}}
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13564#comment:5>
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