[SciPy-user] maximum_filter1d size parameter

Rick Giuly rgiuly@gmail....
Sun Mar 8 18:25:20 CDT 2009


Thanks Josef, that explains it. What I will probably do is use a size 
twice as large as the number of rows.

-Rick

josef.pktd@gmail.com wrote:
> On Sun, Mar 8, 2009 at 2:22 AM, Rick Giuly <rgiuly@gmail.com> wrote:
>> Hello All,
>>
>> It seems I'm not understanding the "size" parameter for
>> maximum_filter1d. The documentation says size is the "length along which
>> to calculate 1D maximum"
>>
>> Starting with this array:
>>  >>> a
>> array([[1, 2, 3],
>>        [4, 1, 1],
>>        [1, 6, 7]])
>>
>>
>> Because there are 3 rows in the matrix, it seems to me that with size
>> set to 3, the result of the filter would be:
>> array([[4, 6, 7],
>>        [4, 6, 7],
>>        [4, 6, 7]])
>>
>>
>> But the result is this:
>>
>>  >>> maximum_filter1d(a, 3, axis=0)
>> array([[4, 2, 3],
>>        [4, 6, 7],
>>        [4, 6, 7]])
>>
>>
>> I don't see why.
>>
>> Any help is appreciated.
>>
>> -rick
> 
> The filter is centered at the current point (keyword order=0), so at
> the boundary it uses only the boundary point and the point next to it.
> There are different modes (keyword mode), but none of them seem to
> deliver what you want.
> 
> I tried different mode and order combinations, but it seems changing
> the order at the boundaries to use the filter in one direction only is
> not possible.
> 
> Josef
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