numpy-discussion

[Numpy-discussion] numpy putmask() method and a scalar.

[Christopher B. <Chr...@no...>]

Hi all,

I was just trying to use the putmask() method to replace a bunch of 
values with the same value and got and error, where the putmask() 
function works fine:

 >>> import numpy as N
 >>> a = N.arange(5)
 >>> a
array([0, 1, 2, 3, 4])
 >>> a.putmask(a > 3, 3)
Traceback (most recent call last):
   File "<stdin>", line 1, in ?
ValueError: putmask: mask and data must be the same size

 >>> N.putmask(a, a > 3, 3)
 >>> a
array([0, 1, 2, 3, 3])

and:

 >>> help (N.ndarray.putmask)
putmask(...)
     a.putmask(values, mask) sets a.flat[n] = v[n] for each n where 
mask.flat[n] is TRUE. v can be scalar.

indicates that it should work.

-Chris


-- 
Christopher Barker, Ph.D.
Oceanographer
                                     		
NOAA/OR&R/HAZMAT         (206) 526-6959   voice
7600 Sand Point Way NE   (206) 526-6329   fax
Seattle, WA  98115       (206) 526-6317   main reception

Chr...@no...

Re: [Numpy-discussion] numpy putmask() method and a scalar.

[Sasha <nd...@ma...>]

Do we really need the putmask method?  With fancy indexing the obvious
way to do it is

>>> a[a>3] =3D 3

and it works fine.   Maybe we can drop putmask method before 1.0
instead of fixing the bug.

On 5/1/06, Christopher Barker <Chr...@no...> wrote:
> Hi all,
>
> I was just trying to use the putmask() method to replace a bunch of
> values with the same value and got and error, where the putmask()
> function works fine:
>
>  >>> import numpy as N
>  >>> a =3D N.arange(5)
>  >>> a
> array([0, 1, 2, 3, 4])
>  >>> a.putmask(a > 3, 3)
> Traceback (most recent call last):
>    File "<stdin>", line 1, in ?
> ValueError: putmask: mask and data must be the same size
>
>  >>> N.putmask(a, a > 3, 3)
>  >>> a
> array([0, 1, 2, 3, 3])
>
> and:
>
>  >>> help (N.ndarray.putmask)
> putmask(...)
>      a.putmask(values, mask) sets a.flat[n] =3D v[n] for each n where
> mask.flat[n] is TRUE. v can be scalar.
>
> indicates that it should work.
>
> -Chris
>
>
> --
> Christopher Barker, Ph.D.
> Oceanographer
>
> NOAA/OR&R/HAZMAT         (206) 526-6959   voice
> 7600 Sand Point Way NE   (206) 526-6329   fax
> Seattle, WA  98115       (206) 526-6317   main reception
>
> Chr...@no...
>
>
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Re: [Numpy-discussion] numpy putmask() method and a scalar.

[John H. <jdh...@ac...>]

>>>>> "Sasha" == Sasha  <nd...@ma...> writes:

    Sasha> Do we really need the putmask method?  With fancy indexing
    Sasha> the obvious way to do it is

    >>>> a[a>3] = 3

    Sasha> and it works fine.  Maybe we can drop putmask method before
    Sasha> 1.0 instead of fixing the bug.

I'm +1 for backwards compatibility with the Numeric API where the cost
of a fix isn't too painful.  The way to speed numpy adoption is to
make old Numeric code "just work" where possible with the new API.

Bear in mind that many people may not even begin the port attempt
until well after numpy 1.0.

JDH

Re: [Numpy-discussion] numpy putmask() method and a scalar.

[Keith G. <kwg...@gm...>]

On 5/1/06, Sasha <nd...@ma...> wrote:
> Do we really need the putmask method?  With fancy indexing the obvious
> way to do it is
>
> >>> a[a>3] =3D 3

That would be a great example for the NumPy for Matlab Users page.

http://www.scipy.org/NumPy_for_Matlab_Users

Re: [Numpy-discussion] numpy putmask() method and a scalar.

[Christopher B. <Chr...@no...>]

John Hunter wrote:
>     Sasha> Do we really need the putmask method?  With fancy indexing
>     Sasha> the obvious way to do it is
> 
>     >>>> a[a>3] = 3

Duh! I totally forgot about that, despite the fact that that was the one 
thing I missed when moving form Matlab to Numeric a few years back.

> I'm +1 for backwards compatibility with the Numeric API where the cost
> of a fix isn't too painful.

I agree, however, does Numeric have a putmask() method? or only a 
putmask function? The numpy putmask function works fine.

Still, this looks like a bug that may well apply to other methods, so 
it's probably worth fixing.

-Chris



-- 
Christopher Barker, Ph.D.
Oceanographer
                                     		
NOAA/OR&R/HAZMAT         (206) 526-6959   voice
7600 Sand Point Way NE   (206) 526-6329   fax
Seattle, WA  98115       (206) 526-6317   main reception

Chr...@no...