Re: IndexError when trying to read masked value from variable

Hi Oleksandr,

While I have to admit I don't understand your entire response, for
example the bit about reversing elements, your suggestion of accessing
the variable with "[:]" worked! I changed line 4 of my code so it
reads:

zval = f.variables["zval"][:] # instead of zval = f.variables["zval"]

Now, when I run the code, it doesn't fail here like before:

zvalDirectMissingVal = zval[0, 1, 64387]

When I print zvalDirectMissingVal, then I see "---", which is correct.

Perhaps you were suggesting something slightly different, but in
either case the mystery seems somewhat solved. Still, it's kind of
strange. If I was able to read most values of zval without the "[:]"
at the end of the variable extraction, then I don't understand why I
couldn't read all values this way.

Thanks for your help,

Carmen

On Tue, Jul 3, 2012 at 6:05 PM, Oleksandr Huziy <guziy.sasha@gmail.com> wrote:
> Hi Carmen,
>
> I am not sure if this is important, but I don't see the point in your code
> as described here:
>
> Get the data in a variable object into a NumPy array
>
> If the variable is not scalar (rank > 0):
>
> data = f.variables.['varName'][:]
>
> or
>
> data = f.variables.['varName'],get_value()
>
> Assuming the shape of the variable is (5,20,30) get a slice along the first
> element of the first dimension:
>
> var = f.variables.['varName']
> data = var[0]
>
> Get the same slice but reverse the elements of the second dimension. The
> following two statements are equivalent:
>
> data = var[0,::-1,:]
> data = var[0,19::-1,:]
>
>
> I would test it myself but Nio (which I installed using macports), does not
> work on my system.
>
> Another option for you would be to try netcdf4-python
>
> Cheers
>
> --
> Oleksandr (Sasha) Huziy
>
>
>
> 2012/7/3 Carmen St. Jean <carmen.stjean@noaa.gov>
>>
>> Hello all,
>>
>> I'm getting this strange error message when I attempt to run the
>> attached code with this input file
>>
>> (http://jetstreak.unh.edu/netcdf/nos.creofs.fields.nowcast.20120625.t12z.nc,
>> it is over one GB in size):
>>
>> Traceback (most recent call last):
>> File "creofstest.py", line 22, in <module>
>> zvalDirectMissingVal = zval[0, 1, 64387]
>> File "/usr/local/lib/python2.7/site-packages/PyNIO/Nio.py", line
>> 305, in __getitem__
>> ret = _fill_value_to_masked(self,ret)
>> File "/usr/local/lib/python2.7/site-packages/PyNIO/Nio.py", line
>> 283, in _fill_value_to_masked
>> a = ma.masked_where(a == self.__dict__['_FillValue'],a,copy=0)
>> File "/usr/local/lib/python2.7/site-packages/numpy/ma/core.py", line
>> 1802, in masked_where
>> " (got %s and %s)" % (cshape, ashape))
>> IndexError: Inconsistant shape between the condition and the input
>> (got (1,) and ())
>>
>> My code is very simple; it's just trying to access the zval variable
>> at different valid indices.
>>
>> I can directly access a specific value from the zval variable that
>> happens to not contain the missing value (e.g., zval[0, 0, 64387])
>> without a problem. But when I try to directly access a value that I
>> know to be a missing value (e.g., zval[0, 1, 64387]), then I get the
>> above error.
>>
>> I am, however, able to indirectly access that value zval[0, 1, 64387]
>> by saving zval[0, :, 64387] to a new variable and taking the 1st index
>> of that. This correctly prints out as a missing value.
>>
>> Does anyone have any ideas of why this might be happening?
>>
>> Thanks,
>>
>> Carmen
>>
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Received on Thu Jul 5 14:43:58 2012