[SciPy-User] Select rows according to cell value

Juan Luis Cano Rodríguez juanlu001@gmail....
Tue Nov 13 10:07:19 CST 2012


I am loading some tabular data of the form

  alt    temp    press    dens
  10.0    223.3    26500    0.414
  10.5    220.0    24540    0.389
  11.0    216.8    22700    0.365
  11.5    216.7    20985    0.337
  12.0    216.7    19399    0.312
  12.5    216.7    17934    0.288
  13.0    216.7    16579    0.267
  13.5    216.7    15328    0.246
  14.0    216.7    14170    0.228

into an ordinary NumPy array using np.loadtxt. I would like though to
select the rows according to the altitude level, that is:

    >>> data = np.loadtxt('data.txt', skiprows=1)
    >>> altitudes = [10.5, 11.5, 14.0]
    >>> d = ...  # some simple syntax involving data and altitudes
    >>> d
    10.5    220.0    24540    0.389
    11.5    216.7    20985    0.337
    14.0    216.7    14170    0.228

I have tried a cumbersome expression which traverses all the array, then
uses a list comprehension, converts to an array... but I'm sure there must
be a simpler way. I've also looked at argwhere. Or maybe I should use
pandas?

Thank you in advance.
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