[Numpy-discussion] Reading a big netcdf file
Christopher Barker
Chris.Barker at noaa.gov
Thu Aug 4 15:26:29 EDT 2011
On 8/4/11 10:02 AM, Christopher Barker wrote:
> On 8/4/11 8:53 AM, Jeff Whitaker wrote:
>> Kiko: I think the difference may be that when you read the data with
>> netcdf4-python, it tries to unpack the short integers to a float32
>> array.
>
> Jeff, why is that? is it an netcdf4 convention? I always thought that
> the netcdf data model matched numpy's quite well, including the clear
> choice and specification of data type. I guess I've mostly used float
> data anyway, so hadn't noticed this, but ti comes as a surprise to me!
>
> > gebco4.set_automaskandscale(False)
OK -- looked at this a bit more, and see in the OP's ncdump:
variables:
short z(xysize) ;
z:scale_factor = 1. ;
z:add_offset = 0. ;
z:node_offset = 0 ;
so I presume netCDF4 is seeing the scale_factor and offsets, and thus
converting to float.
In this case, the scale factor is 1.0, and the offsets are 0.0, so there
isn't any need to convert, but that may be too smart!
-Chris
--
Christopher Barker, Ph.D.
Oceanographer
Emergency Response Division
NOAA/NOS/OR&R (206) 526-6959 voice
7600 Sand Point Way NE (206) 526-6329 fax
Seattle, WA 98115 (206) 526-6317 main reception
Chris.Barker at noaa.gov
More information about the NumPy-Discussion
mailing list