[Numpy-discussion] python array

[Sudheer Joseph]

Sorry,
           The below solution I thoght working was not working but was just giving array size.

--------------------------------------------
On Fri, 14/3/14, Sudheer Joseph <sudheer.joseph at yahoo.com> wrote:

 Subject: Re: [Numpy-discussion] python array
 To: "Discussion of Numerical Python" <numpy-discussion at scipy.org>
 Date: Friday, 14 March, 2014, 1:09 AM
 
 Thank you very much Nicolas and
 Chris,
                
              The
 hint was helpful and from that I treid below steps ( a crude
 way I would say) and getting same result now
 
 I have been using abs available by default and it is the
 same with numpy.absolute( i checked).
 
 nr= ((r2010>r2010.min()) & (r2010<r2010.max()))
 nr[nr<.5].shape
 Out[25]: (33868,)
 anr=numpy.absolute(nr)
 anr[anr<.5].shape
 Out[27]: (33868,)
 
 This way I used may have problem when mask used has values
 which can affect the min max operation.
 
 So I would like to know if there is a standard formal (
 python/numpy) way to handle masked array when they need to
 be subjected to boolean operations.
 
 with best regards,
 Sudheer
 
 
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 --------------------------------------------
 On Thu, 13/3/14, Chris Barker - NOAA Federal <chris.barker at noaa.gov>
 wrote:
 
  Subject: Re: [Numpy-discussion] python array
  To: "Discussion of Numerical Python" <numpy-discussion at scipy.org>
  Date: Thursday, 13 March, 2014, 11:53 PM
  
  On Mar 13, 2014, at 9:39 AM, Nicolas
  Rougier <Nicolas.Rougier at inria.fr>
  wrote:
  
  >
  > Seems to be related to the masked values:
  
  Good hint -- a masked array keeps the "junk" values in the
  main array.
  
  What "abs" are you using -- it may not be mask-aware. (
 you
  want a
  numpy abs anyway)
  
  Also -- I'm not sure I know what happens with Boolean
  operators on
  masked arrays when you use them to index. I'd investigate
  that.
  (sorry, not at a machine I can play with now)
  
  Chris
  
  
  > print r2010[:3,:3]
  > [[-- -- --]
  > [-- -- --]
  > [-- -- --]]
  >
  > print abs(r2010)[:3,:3]
  > [[-- -- --]
  > [-- -- --]
  > [-- -- --]]
  >
  >
  > print r2010[ r2010[:3,:3] <0 ]
  > [-- -- -- -- -- -- -- -- --]
  >
  > print r2010[ abs(r2010)[:3,:3] < 0]
  > []
  >
  > Nicolas
  >
  >
  >
  > On 13 Mar 2014, at 16:52, Sudheer Joseph <sudheer.joseph at yahoo.com>
  wrote:
  >
  >> Dear experts,
  >>             
         I am encountering a strange
  behaviour of python data array as below. I have been
 trying
  to use the data from a netcdf file(attached herewith) to
 do
  certain calculation using below code. If I take absolute
  value of the same array and look for values <.5  I
  get a different value than the original array. But the
 fact
  is that this particular case do not have any negative
 values
  in the array( but there are other files where it can have
  negative values so the condition is put). I do not see any
  reason for getting different numbers for values <.5 in
  case of bt and expected it to be same as that of r2010. If
  any one has a guess on what is behind this behaviour
 please
  help.
  >>
  >>
  >> In [14]: from netCDF4 import Dataset as nc
  >>
  >> In [15]: nf=nc('r2010.nc')
  >> In [16]: r2010=nf.variables['R2010'][:]
  >> In [17]: bt=abs(r2010)
  >> In [18]: bt[bt<=.5].shape
  >> Out[18]: (2872,)
  >> In [19]: r2010[r2010<.5].shape
  >> Out[19]: (36738,)
  >>
  >>
  >> bt.min()
  >> Out[20]: 0.0027588337040836768
  >>
  >> In [21]: bt.max()
  >> Out[21]: 3.5078965479057089
  >> In [22]: r2010.max()
  >> Out[22]: 3.5078965479057089
  >> In [23]: r2010.min()
  >> Out[23]: 0.0027588337040836768
  >>
  >>
  >>
  >>
  ***************************************************************
  >> Sudheer Joseph
  >> Indian National Centre for Ocean Information
  Services
  >> Ministry of Earth Sciences, Govt. of India
  >> POST BOX NO: 21, IDA Jeedeemetla P.O.
  >> Via Pragathi Nagar,Kukatpally, Hyderabad;
 Pin:5000
  55
  >> Tel:+91-40-23886047(O),Fax:+91-40-23895011(O),
  >>
  Tel:+91-40-23044600(R),Tel:+91-40-9440832534(Mobile)
  >> E-mail:sjo.India at gmail.com;sudheer.joseph at yahoo.com
  >> Web- http://oppamthadathil.tripod.com
  >>
  ***************************************************************<r2010.nc>_______________________________________________
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  >> NumPy-Discussion at scipy.org
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