[gradsusr] Accessing data chunks via GrADS data server

[Marsh, Kieren [FGUAE]]

Jennifer

Thanks for the reply.

I have been using the method you describe however, the GrADS Data Server I am accessing (I don't administer it) is breaking my request midway through GrADS defining process. The server admin is telling me the GDS is reporting that I am making too many data requests (subset operation failed; creation of child process failed    -  Cannot run program "nice": error=24, Too many open files).

Obviously you're not in receipt of all the facts but as far as I can tell everything is being done correctly on my side. Can you think of any possible causes of this?

Thanks again for all your efforts.

Kieren Marsh


From: gradsusr-bounces at gradsusr.org [mailto:gradsusr-bounces at gradsusr.org] On Behalf Of Jennifer Adams
Sent: 28 May 2014 23:18
To: GrADS Users Forum
Subject: Re: [gradsusr] Accessing data chunks via GrADS data server


On May 27, 2014, at 8:45 PM, Marsh, Kieren [FGUAE] wrote:


Can someone please explain to me how the bracketed notation works to extract data from a GDS. By this I mean the following:


http://metserver:9090/dods/neww3/neww3.00z.ascii?htsgwsfc[0:20][0:40][110][72<http://metserver:9090/dods/neww3/neww3.00z.ascii?htsgwsfc%5b0:20%5d%5b0:40%5d%5b110%5d%5b72>]

which extracts htsgwsfc over ensemble members 1-21 (0-20 when zero based), time values 0-40 at x=110 and y=72 and gives an ascii text file I can grab using something like wget.


Am I able to use this kind of notation in GrADS scripts to access a chunk of data that I can define to a variable?


e.g.


'define myvar = http://metserver:9090/dods/neww3/neww3.00z.?htsgwsfc[0:20][0:40][110][72<http://metserver:9090/dods/neww3/neww3.00z.?htsgwsfc%5b0:20%5d%5b0:40%5d%5b110%5d%5b72%5d'>]'


All combinations I try don't work and I can't find any documentation on it.

The way to do this is to open the URL, then set the dimension environment in GrADS, then define your variable.
Something like this:

'sdfopen http://metserver:9090/dods/neww3/neww3.00z'
'set e 1 21'
'set t 1 41'
'set x 110'
'set y 72'
'myvar=htsgwsfc'

--Jennifer





I have looked at the documentation for access using the curly bracket notation, e.g.:
http://metserver:9090/dods/_expr_{neww3/neww3.t00z}{htsgwsfc}{73:73,111:111,1:1,00Z20MAY2014:00Z25MAY2014}<http://metserver:9090/dods/_expr_%7bneww3/neww3.t00z%7d%7bhtsgwsfc%7d%7b73:73,111:111,1:1,00Z20MAY2014:00Z25MAY2014%7d>


...but I don't seem to be able to capture the ensemble dimension using this format.


Any help will be greatly appreciated.


Kieren
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Jennifer M. Adams
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