On 3/7/11 11:42 AM, Christopher Barker wrote: > On 3/7/11 9:33 AM, Francesc Alted wrote: >> A Monday 07 March 2011 18:28:11 Christopher Barker escrigué: >>> I'm setting out to write some code to access and work with ragged >>> arrays stored in netcdf files. It dawned on me that ragged arrays >>> are not all that uncommon, so I'm wondering if any of you have any >>> code you've developed that I could learn-from borrow from, etc. >> A list of numpy arrays would not be enough? Or you want something more >> specific? > Maybe that would, but in mapping to the netcdf data model, I'm thinking > more like a big 1-d numpy array, with a way to index into it. Also, that > would allow you to do some math with the arrays, if the broad casting > made sense, anyway. > > But now that you've entered the conversation, does HDF and/or pytables > have a standard way of dealing with this? > > On 3/7/11 9:37 AM, Jeff Whitaker wrote: >> Chris: The netcdf4-python modules reads netcdf vlen arrays > arethose a netcdf4 feature? Chris:
Yes, although I don't think many people are using it. See section 10 in http://netcdf4-python.googlecode.com/svn/trunk/docs/netCDF4-module.html. > So far, I'm still workign with netcdf3 -- > though this could be a compelling reason to move on! > > We've talked about this some on the CF list, and I don't think anyone > brought that up. > >> and returns >> numpy object arrays, where the elements of the object arrays are >> themselves 1d numpy arrays. I don't think there is any other way to do >> it. In your example, the 'ragged' array would be a 1d numpy array with >> dtype='O', and the individual elements would be 1d numpy arrays with >> dtype=int. Of course, these arrays are very awkward to deal with and >> operations will be slow. > Depends some of the operations, but yes. > > That still may be the best option, but I'm exploring others. > > is a "vlen array" stored contiguously in netcdf? Probably, although I don't know for sure what the underlying HDF5 layer is doing. -Jeff > -Chris > > > > -- Jeffrey S. Whitaker Phone : (303)497-6313 Meteorologist FAX : (303)497-6449 NOAA/OAR/PSD R/PSD1 Email : jeffrey.s.whita...@noaa.gov 325 Broadway Office : Skaggs Research Cntr 1D-113 Boulder, CO, USA 80303-3328 Web : http://tinyurl.com/5telg _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
