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970110: netCDF

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  • Subject: 970110: netCDF
  • Date: Fri, 10 Jan 97 15:23:08 -0700
Bill,

> To: address@hidden
> From: Bill Spotz <address@hidden>
> Organization: UCAR/NCAR/SCD
> Keywords: 199701102032.NAA01266

In the above message you wrote:

> The netCDF library is not behaving the way I am expecting it to, and I
> was hoping you could help.  I have some two-dimensional data, and I am
> trying to write a hyperslab which does not include the boundary.  I
> want to get the default missing value there so that an NCAR Graphics
> contour plot of the data will leave the boundary data unplotted.
> 
> I am using the FORTRAN interface and have included a short program
> which recreates the problem.  My intent is to write the variable
> "info" such that the zero's get written and the minus one's do not.
> But that is not the result I get.
> 
> Thanks in advance,
> Bill Spotz
> 
> =====================================================================
>       program junk
> 
>       integer IMAX
>       integer JMAX
>       parameter (IMAX=11, JMAX=11)
> 
>       double precision info(IMAX,JMAX)
>       integer i
>       integer j
> 
>       integer start(3)
>       integer count(3)
>       integer vdim(3)
>       integer infoid
> 
>       integer ncid
>       integer ier
> 
>       include 'netcdf.inc'
> 
>       do 20 i = 1, IMAX
>         do 10 j = 1, JMAX
>           if (i.eq.1 .or. i.eq.IMAX .or. j.eq.1 .or. j.eq.JMAX) then
>             info(i,j) = -1.0
>           else
>             info(i,j) = 0.0
>           end if
>    10   continue
>    20 continue
> 
>       start(1) = 2
>       start(2) = 2
>       start(3) = 1
>       count(1) = IMAX-2
>       count(2) = JMAX-2
>       count(3) = 1
> 
>       ncid = nccre("info.cdf",NCCLOB,ier)
>       vdim(1) = ncddef(ncid,'i',IMAX,ier)
>       vdim(2) = ncddef(ncid,'j',JMAX,ier)
>       vdim(3) = ncddef(ncid,'iterate',NCUNLIM,ier)
>       infoid = ncvdef(ncid,'info',NCDOUBLE,3,vdim,ier)
>       call ncendf(ncid,ier)
>       call ncvpt(ncid,infoid,start,count,info,ier)
>       call ncclos(ncid,ier)
> 
>       stop
>       end
> 
> ------- End of Forwarded Message

What you need to realize is that the `start' and `count' arrays refer to
the external hyperslab and not the internal one.  The netCDF library is
going to start writing from the first element of the `info' array (i.e.
info(1,1)) and not from where you think (i.e. info(2,2)).  You should
change the output code to something that writes the array one J-line at
a time, e.g.

        start(1) = 2
        start(3) = 1
        count(1) = IMAX-2
        count(2) = 1
        count(3) = 1
        do 30, j = 2, JMAX-1
            start(2) = j
            call ncvpt(ncid,infoid,start,count,info(2,j),ier)
30      continue

Please let me know if this helps.
--------
Steve Emmerson   <address@hidden>