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Re: Reading part of a netcdf file? [message #86021 is a reply to message #86016]

Tue, 24 September 2013 09:46

Paul Van Delst[1]
Messages: 1157
Registered: April 2002

Senior Member

See:
http://www.exelisvis.com/docs/NCDF_VARGET.html

Similar to what David said, the COUNT and OFFSET keywords are the ones
that should do the job for you (don't think you need STRIDE).

Just of the top of my head you'd need something like
COUNT=[144, 72, 17, X]
and for the first read
OFFSET=[0,0,0,0]
For the second read of X timesteps,
OFFSET=[0,0,0,X]
third,
OFFSET=[0,0,0,X*2]
etc..

I think I got the general idea right (anyone?). The X-related numbers
may be off by one since count is 1-based and offset is 0-based and I
always get 'em mixed up.

cheers,

paulv

On 09/24/13 11:26, rjp23@le.ac.uk wrote:
> I have a very large (22GB) netcdf file and I was hoping there was
> some way to read part of it at a time into IDL but I can't figure out
> how.
>
> For example, I have this variable:
>
> Var FLOAT = Array[144, 72, 17, 32161]
>
> The 4th dimension is time, i.e. the are 32161 timesteps.
>
> Is it possible to read only the first X in one go, then read the next
> X, etc meaning that less is stored in memory at once?
>
> Cheers
>
> Rob
>

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[Message index]

		Reading part of a netcdf file? By: rjp23 on Tue, 24 September 2013 08:26
		Re: Reading part of a netcdf file? By: David Fanning on Tue, 24 September 2013 09:06
		Re: Reading part of a netcdf file? By: rjp23 on Tue, 24 September 2013 09:11
		Re: Reading part of a netcdf file? By: David Fanning on Tue, 24 September 2013 09:31
		Re: Reading part of a netcdf file? By: David Fanning on Tue, 24 September 2013 09:40
		Re: Reading part of a netcdf file? By: Paul Van Delst[1] on Tue, 24 September 2013 09:46
		Re: Reading part of a netcdf file? By: Michael Galloy on Tue, 24 September 2013 13:01

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