[Numpy-discussion] Deleting a row from a matrix

Bill Baxter wbaxter at gmail.com
Sat Aug 26 07:13:15 CDT 2006


On 8/26/06, Travis Oliphant <oliphant.travis at ieee.org> wrote:
>
>
> I've come up with adding the functions (not methods at this point)
>
> deletefrom
> insertinto


"delete" and "insert" really would be better.   The current "insert"
function seems inaptly named.  What it does sounds more like "overlay" or
"set_masked".

... or the existing "putmask" which I see does a similar thing.

Actually there seems to be a little doc-bug there or something.
numpy.insert claims it differs from putmask in that it only accepts a vector
of values with same number of vals as the # of non-zero entries in the mask,
but a quick test revals it's quite happy with a different number and cycles
through them.

In [31]: a = numpy.zeros((3,3))
In [32]: numpy.insert(a, [[0,1,0],[1,0,0],[1,0,0]], [4,5])
In [33]: a
Out[33]:
array([[ 0.,  4.,  0.],
       [ 5.,  0.,  0.],
       [ 4.,  0.,  0.]])

Anyway, in the end nothing has really been inserted, existing entries have
just been replaced.

So "insert" seems like a much better name for a function that actually puts
in a new row or column.

--bb
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