Re: reading all the variables from a netCDF when the variable names are unknown (or too many)

Jonathan,

Do you need to have all the variables in memory at the same time, or
can you just process them one at a time from the input file to the
output file(s)? The second has a much easier answer than the first.
  A little more information about the nature of your application is
needed.

Dave Allured
CU/CIRES Climate Diagnostics Center (CDC)
http://cires.colorado.edu/science/centers/cdc/
NOAA/ESRL/PSD, Climate Analysis Branch (CAB)
http://www.cdc.noaa.gov/psd1/

Jonathan Vigh wrote:
>
> Greetings NCL'ers,
> I'd like to read in all the variables from a netCDF file in a
> general way because there are 177 of them. I understand how to query the
> file and get a list of variable names, and I even understand how to
> reference the variable using:
> fin->$varnames$
>
> What I am confused about is what to assign this to. I'd like to avoid
> having to type out 177 lines to read in each variable if possible. But
> if I didn't even know the variable names in advance, I'd still like to
> know how to do this.
>
> Maybe I've missed something really basic, but I couldn't seem to find
> anything from the documentation. If anyone has an idea, I'd be most
> grateful. It would be nice if NCL could simply make all the variables in
> a netCDF file available without having to go through this step, so maybe
> this could be the prototype for a new function that does this.
>
> Thanks,
> Jonathan
>
>
> begin
> processed_filename = systemfunc("cd " + processed_data_directory + ";
> ls " + stormid + "*.nc")
> fin = addfile(processed_data_directory + processed_filename,"r") ;
> open output netCDF file
>
> ; query the file to see what variables it contains and what the sizes of
> the file dimensions are
> varnames = getfilevarnames(fin) ; Returns an array of file
> variable names in the file
> filedimsizes = getfiledimsizes(fin) ; Returns a list of the
> sizes of all the dimensions in the file.
>
> ; query all the named variables in the file
> vartypes = getfilevartypes(fin,varnames) ; Returns the type of
> each variable name listed. A missing value is returned for any variable
> name that doesn't exist in the file.
>
>
> ; loop through all the variables, query them, and read them in
> nvars = dimsizes(varnames)
> do ivar = 0, nvars-1
> print("Reading variable ivar = "+ivar+" "+vartypes(ivar)+"
> "+varnames(ivar))
> ???? = fin->$varnames(ivar)$ ; I understand how to
> read in a variable from a file if I don't know the variable name in
> advance, but how can I assign it to a variable without typing the
> variable's name?
> end do
>
> end
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Received on Tue Feb 24 2009 - 13:24:17 MST