[Numpy-discussion] Structured array sorting

[Thomas Robitaille]

I am having trouble sorting a structured array - in the example below, sorting 
by the first column (col1) seems to work, but not sorting by the second column 
(col2). Is this a bug?

I am using numpy svn r8071 on MacOS 10.6.

Thanks for any help,

Thomas

Python 2.6.1 (r261:67515, Jul  7 2009, 23:51:51) 
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import numpy as np
>>> data = np.array([('a ', 2.), ('b', 4.), ('d', 3.), ('c', 1.)],
... dtype=[('col1', '|S5'), ('col2', '>f8')])
>>> 
>>> data
array([('a ', 2.0), ('b', 4.0), ('d', 3.0), ('c', 1.0)], 
  dtype=[('col1', '|S5'), ('col2', '>f8')])
>>> data.sort(order=['col1'])
>>> data
array([('a ', 2.0), ('b', 4.0), ('c', 1.0), ('d', 3.0)], 
  dtype=[('col1', '|S5'), ('col2', '>f8')])
>>> data.sort(order=['col2'])
>>> data
array([('a ', 2.0), ('d', 3.0), ('b', 4.0), ('c', 1.0)], 
  dtype=[('col1', '|S5'), ('col2', '>f8')])


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Re: [Numpy-discussion] Structured array sorting

[Warren Weckesser]

Looks like 'sort' is not handling endianess of the column data 
correctly.  If you change the type of the floating point data to 'i2')])

In [141]: z.sort(order='num')

In [142]: z
Out[142]:
array([(255,), (0,), (256,), (1,), (258,)],
  dtype=[('num', '>i2')])

In [143]: np.__version__
Out[143]: '1.3.0'
-

Sorting works as expected with a simple array of short ints:

-
In [152]: w = np.array([0,258, 3, 255], dtype=' I am having trouble sorting a structured array - in the example below, 
> sorting by the first column (col1) seems to work, but not sorting by the 
> second column (col2). Is this a bug?
>
> I am using numpy svn r8071 on MacOS 10.6.
>
> Thanks for any help,
>
> Thomas
>
> Python 2.6.1 (r261:67515, Jul  7 2009, 23:51:51) 
> [GCC 4.2.1 (Apple Inc. build 5646)] on darwin
> Type "help", "copyright", "credits" or "license" for more information.
>   
 import numpy as np
 data = np.array([('a ', 2.), ('b', 4.), ('d', 3.), ('c', 1.)],
 
> ... dtype=[('col1', '|S5'), ('col2', '>f8')])
>   
 data
 
> array([('a ', 2.0), ('b', 4.0), ('d', 3.0), ('c', 1.0)], 
>   dtype=[('col1', '|S5'), ('col2', '>f8')])
>   
 data.sort(order=['col1'])
 data
 
> array([('a ', 2.0), ('b', 4.0), ('c', 1.0), ('d', 3.0)], 
>   dtype=[('col1', '|S5'), ('col2', '>f8')])
>   
 data.sort(order=['col2'])
 data
 
> array([('a ', 2.0), ('d', 3.0), ('b', 4.0), ('c', 1.0)], 
>   dtype=[('col1', '|S5'), ('col2', '>f8')])
>
>
> ___
> NumPy-Discussion mailing list
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>   

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Re: [Numpy-discussion] Structured array sorting

[Thomas Robitaille]

Warren Weckesser-3 wrote:
> 
> Looks like 'sort' is not handling endianess of the column data 
> correctly.  If you change the type of the floating point data to ' the sort works.
> 

Thanks for identifying the issue - should I submit a bug report?

Thomas
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Re: [Numpy-discussion] Structured array sorting

[Charles R Harris]

On Mon, Jan 18, 2010 at 6:39 AM, Thomas Robitaille <
thomas.robitai...@gmail.com> wrote:

>
>
> Warren Weckesser-3 wrote:
> >
> > Looks like 'sort' is not handling endianess of the column data
> > correctly.  If you change the type of the floating point data to ' > the sort works.
> >
>
> Thanks for identifying the issue - should I submit a bug report?
>
>
Yes.

Chuck
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