[Numpy-discussion] Re: [SciPy-user] Messing with missing values

Paul F. Dubois paul at pfdubois.com
Mon Feb 27 12:55:04 CST 2006


Some things don't make sense for missing value arrays. For example, 
FFT's. Median does not make sense if you fill so you have to use 
compress. I think for each operation you must decide what you mean 
exactly. If it fits the "easy" wrapper model, you can do that, but 
otherwise, you have to code it.

Sasha wrote:
> On 2/27/06, pgmdevlist at mailcan.com <pgmdevlist at mailcan.com> wrote:
>> ...
>> I remmbr a message a couple of weeks ago wondering whether ma should be kpet
>> uptodate with the rest of numpy (and of course, I can't find the reference
>> right now). What's the status on ma ?
>>
> 
> Ma will be supported in numpy.  See FAQ
> <http://new.scipy.org/Wiki/FAQ> "Does NumPy support nan ("not a
> number")?."
> 
> Ma development page is at
> http://projects.scipy.org/scipy/numpy/wiki/MaskedArray .
> Feel free to add contents there.  I would welcome a section listing
> numpy functions that are still not available in ma.
> 
> 
>> Let's take the `median` example for 2D arrays.
> 
> Median is one of those examples where Paul's recommendation does not
> work because missing values should be ignored rather than filled.  For
> example, in R median has two modes: to ignore missing values and to
> return missing value if any value is missing:
> 
>> median(c(1,NA))
> [1] NA
>> help(median)
>> median(c(1,NA),na.rm=TRUE)
> [1] 1
>> median(c(1,0))
> [1] 0.5
> 
> 
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