| Re: HDF_SD_GETACCESS: No content in variable, error [message #71787 is a reply to message #71782] |
Wed, 21 July 2010 09:38   |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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aa8533 writes:
> Hi - I'm trying to make a program which automatically runs through
> 100s of images (MODIS Fire data) and extracts data at a particular
> point. The program works fine where there is data to extract (in the
> case below, when there is data in FP_Sample) but halts for an image
> where there is none with message "Array dimensions must be greater
> than 0".
>
> Extract of code is:
>
> sd=hdf_sd_start(fileName)
> index=hdf_sd_nametoindex(sd,'FP_sample')
> sds=hdf_sd_select(sd,index)
> hdf_sd_getdata,sds,sample <------------------ Halts with message
> here
>
> Is there a way to test the size of the variable (in this case Sample)
> and if, say it's -1 (no data) then skip the last line of this code?
I opened each of the two files you sent me up in my
NCDF_Browser program and I could immediately see that
FP_sample in the file that causes the problem has
a dimension of 0. Obviously, nothing is there, even
though the variable has been defined in the file!
To look for this possibility (I have modified my own
code in ncdf_data__define.pro and it will be on my
web page shortly) you will have to check for a zero
length dimension:
sd=hdf_sd_start(fileName)
index=hdf_sd_nametoindex(sd,'FP_sample')
sds=hdf_sd_select(sd,index)
HDF_SD_GetInfo, sds, DIMS=dims
IF dims[0] NE 0 THEN BEGIN
hdf_sd_getdata,sds,sample
ENDIF
I notice that every variable in that particular data file
has a dimension of 0. That is one very sick puppy! :-)
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")
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