| how to search if a variable exists in a file [message #92002] |
Mon, 28 September 2015 15:25  |
Xiaohua Pan
Messages: 2
Registered: September 2015
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Junior Member |
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Hi all,
I am dealing with a set of stations which unfortunately contain different variables (netcdf formate). For example, Some stations have the variables, say 'temperature' and 'pressure', while some stations only have 'temperature'. When I read data with DO loop the stations, I would like to search the variable first, so I can skip those variables not existing to avoid the crash of program. I found a function of file_search(), but can't find a similar function for a variable. Is there anyone know how to do it? Thanks.
DO i_station = 0, n-1 do begin
DO i_var = 0, 1 do begin
; How to skip the variable if it doesn't exit ????
ENDFOR
ENDFOR
Thanks.
Xiaohua
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| Re: how to search if a variable exists in a file [message #92003 is a reply to message #92002] |
Mon, 28 September 2015 16:25  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Xiaohua Pan writes:
> I am dealing with a set of stations which unfortunately contain
different variables (netcdf formate). For example, Some stations have
the variables, say 'temperature' and 'pressure', while some stations
only have 'temperature'. When I read data with DO loop the stations, I
would like to search the variable first, so I can skip those variables
not existing to avoid the crash of program. I found a function of
file_search(), but can't find a similar function for a variable. Is
there anyone know how to do it? Thanks.
>
> DO i_station = 0, n-1 do begin
> DO i_var = 0, 1 do begin
> ; How to skip the variable if it doesn't exit ????
> ENDFOR
> ENDFOR
If you were to use the netCDF programs in the Coyote Library to work
with your netCDF files, you could use the method HasVar to tell you if a
file contains a variable with a particular name:
http://www.idlcoyote.com/fileio_tips/ncdf_browser.html
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")
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| Re: how to search if a variable exists in a file [message #92004 is a reply to message #92002] |
Tue, 29 September 2015 08:27 |
Paul Van Delst[1]
Messages: 1157
Registered: April 2002
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Senior Member |
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On 09/28/15 18:25, Xiaohua Pan wrote:
> Hi all,
> I am dealing with a set of stations which unfortunately contain
> different variables (netcdf formate). For example, Some stations have
> the variables, say 'temperature' and 'pressure', while some stations
> only have 'temperature'. When I read data with DO loop the stations, I
> would like to search the variable first, so I can skip those variables
> not existing to avoid the crash of program. I found a function of
> file_search(), but can't find a similar function for a variable. Is
> there anyone know how to do it? Thanks.
>
> DO i_station = 0, n-1 do begin
> DO i_var = 0, 1 do begin
> ; How to skip the variable if it doesn't exit ????
> ENDFOR
> ENDFOR
See:
http://www.exelisvis.com/docs/NCDF_VARID.html
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| Re: how to search if a variable exists in a file [message #92006 is a reply to message #92003] |
Tue, 29 September 2015 12:05 |
Xiaohua Pan
Messages: 2
Registered: September 2015
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Junior Member |
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On Monday, September 28, 2015 at 7:25:32 PM UTC-4, David Fanning wrote:
> Xiaohua Pan writes:
>
>> I am dealing with a set of stations which unfortunately contain
> different variables (netcdf formate). For example, Some stations have
> the variables, say 'temperature' and 'pressure', while some stations
> only have 'temperature'. When I read data with DO loop the stations, I
> would like to search the variable first, so I can skip those variables
> not existing to avoid the crash of program. I found a function of
> file_search(), but can't find a similar function for a variable. Is
> there anyone know how to do it? Thanks.
>>
>> DO i_station = 0, n-1 do begin
>> DO i_var = 0, 1 do begin
>> ; How to skip the variable if it doesn't exit ????
>> ENDFOR
>> ENDFOR
>
> If you were to use the netCDF programs in the Coyote Library to work
> with your netCDF files, you could use the method HasVar to tell you if a
> file contains a variable with a particular name:
>
> http://www.idlcoyote.com/fileio_tips/ncdf_browser.html
>
> Cheers,
>
> David
> --
> David Fanning, Ph.D.
> Fanning Software Consulting, Inc.
> Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
> Sepore ma de ni thue. ("Perhaps thou speakest truth.")
Hi David,
It works. Thank you so much!
Xiaohua
For those who may need this information as well,
here is an example:
filename = 'data.nc'
var_name = 'sst'
ncdfObj = Obj_New('NCDF_FILE', filename)
hasVar = ncdfObj -> HasVar(var_name, OBJECT=varObj)
IF hasVar THEN BEGIN
print, ' find the variable ' + var_name
ENDIF ELSE BEGIN
print, " Can't find the variable "+var_name
ENDELSE
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