vj wrote:
> I've tried to post this to the numpy google group but it seems to be
> down.
It is just a redirection to the numpy-discussion@scipy.org list. If you just
tried in the past hour or so, I've discovered that our DNS appears to be down
right now.
> My migration seems to be going well. I currently have one issue
> with using scipy_base.insert.
>
>>>> a = zeros(5)
>>>> mask = zeros(5)
>>>> mask[1] = 1
>>>> c = zeros(1)
>>>> c[0] = 100
>>>> numpy.insert(a, mask, c)
> array([ 100., 0., 100., 100., 100., 0., 0., 0.,
> 0., 0.])
>>>> a
> array([ 0., 0., 0., 0., 0.])
>>>> b
> array([0, 0, 0, 0, 0, 0, 0, 0, 0, 1], dtype=int8)
>>>> mask
> array([ 0., 1., 0., 0., 0.])
>>>> c
> array([ 100.])
>
> I would have expected numpy.insert to update a so that the second
> element in a would be 100.
No, that's not what insert() does. See the docstring:
In [1]: from numpy import *
In [2]: insert?
Type: function
Base Class: <type 'function'>
Namespace: Interactive
File:
/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/numpy-1.0.2.dev3569-py2.5-macosx-10.3-fat.egg/numpy/lib/function_base.py
Definition: insert(arr, obj, values, axis=None)
Docstring:
Return a new array with values inserted along the given axis
before the given indices
If axis is None, then ravel the array first.
The obj argument can be an integer, a slice, or a sequence of
integers.
Example:
>>> a = array([[1,2,3],
... [4,5,6],
... [7,8,9]])
>>> insert(a, [1,2], [[4],[5]], axis=0)
array([[1, 2, 3],
[4, 4, 4],
[4, 5, 6],
[5, 5, 5],
[7, 8, 9]])
The behaviour that you seem to want would be accomplished with the following:
In [3]: a = zeros(5)
In [4]: mask = zeros(5, dtype=bool)
In [5]: mask[1] = True
In [6]: mask
Out[6]: array([False, True, False, False, False], dtype=bool)
In [7]: a[mask] = 100
In [8]: a
Out[8]: array([ 0., 100., 0., 0., 0.])
Note that the mask needs to be a bool array.
--
Robert Kern
"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco
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