[Numpy-discussion] Questions about masked arrays
Pierre GM
pgmdevlist at gmail.com
Tue Oct 6 22:22:26 EDT 2009
On Oct 6, 2009, at 9:54 PM, Gökhan Sever wrote:
>
> > Also say, if I want to replace that one element back to its original
> > state will it use fill_value as 1e+20 or 999999.9999?
>
> What do you mean by 'replace back to its original state' ? Using
> `filled`, you mean ?
>
> Yes, in more properly stated fashion "filled" :)
> I[14]: c.data['Air_Temp'][4]
> O[14]:
> masked_array(data = --,
> mask = True,
> fill_value = 1e+20)
>
>
> I[15]: c.data['Air_Temp'][4].filled()
> O[15]: array(1e+20)
>
> Little buggy, isn't it? It properly fill the whole array:
>
> I[13]: c.data['Air_Temp'].filled()
> O[13]:
> array([ 1.31509000e+01, 1.31309000e+01, 1.31278000e+01,
> 1.31542000e+01, 1.00000000e+06, 1.31539000e+01,
> 1.31387000e+01, 1.00000000e+06, 1.00000000e+06,
> 1.00000000e+06, 1.31107000e+01, 1.31351000e+01,
> 1.32073000e+01, 1.32562000e+01, 1.33533000e+01,
> 1.33889000e+01, 1.34067000e+01, 1.32938000e+01,
> 1.31962000e+01, 1.31248000e+01, 1.30411000e+01,
> 1.29534000e+01, 1.28354000e+01, 1.27392000e+01,
> 1.26725000e+01])
Once again, when you access your 5th element, you get the special
`masked` constant. If you fill this constant, you'll get something
which is probably not what you want. And I would need a *REALLY*
compelling reason to change this behavior, as it's gonna break a lot
of things (the masked constant has been around for a while)
> > > 2-) What is wrong with the arccos calculation? Should not that
>
> Er, I assume it's np.arccos ?
>
> Sorry too much time spent in ipython -pylab :)
Well, i use ipython -pylab regularly as well, but still have the
reflex of using np. ;)
>
> I[18]: arccos?
> Type: ufunc
> Base Class: <type 'numpy.ufunc'>
> String Form: <ufunc 'arccos'>
> Namespace: Interactive
> File: /home/gsever/Desktop/python-repo/numpy/numpy/
> __init__.py
>
>
> Anyway, I'm puzzled. Works like a charm here (r7438 for numpy.ma).
> Could it be that something went wrng with some ufuncs ?
>
> This I don't know :(
>
> I didn't touch
> ma since 09/08 (thanks, svn history), so I don't think it comes from
> here...
>
> Yes, SVN is a very useful invention indeed.
>
> I[6]: numpy.__version__
> O[6]: '1.4.0.dev'
>
> For some reason it doesn't list check-out revision.
I know, and it's bugging me as well. if you have a build directory
somewhere, check numpy/core/__svn_version__.py
> This is the last resort. I will eventually try this if I don't any
> other options left.
I gonna have difficulties fixing something that I don't see broken...
Now, there might be something wrong in my installation. I gonna try to
install 1.3.0 somwehere. say, what Python are you using ?
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