Slices with addfile

From: Marquardt, Christian (christian.marquardt AT XXXXXX)
Date: Thu Jan 15 2004 - 13:05:53 MST


Hello,

I'm more or less new to ncl, so I apologise in advance if I have missed
the obvious...

I'm reading data from a large grib file which contains several variables
on multiple levels and for a number of valid times. The usual approach

  gribfile = addfile(<filename>)
  data = gribfile-><varname>

works fine, but seems to slurp in the full 4d block of data at once (or
am I wrong here?). However, I usually only a slice of the full data set
(say, all times, but a single level only, or a vertical slice, or only
part of the entire time series, or...). So reading the entire data block
at once seems to be unnecessary slow; it also requires huge amounts of
memory.

Is there a way to read only slices of the data? For example, when using
data in a netCDF from a fortran (or so) program, I could specify the
start indices in each dimension, etc.

Thanks a lot,

  Christian.

-- 
Dr Christian Marquardt  Research Scientist
Met Office   FitzRoy Road   Exeter   EX1 3PB   United Kingdom
Tel: +44 (0)1392 88 4820   Fax: +44 (0)1392 885681
E-mail: christian.marquardt AT metoffice.com   http://www.metoffice.com

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