[gradsusr] Utilizing data from text file to make calculation in GrADS

[Charles Seman - NOAA Federal]

Phil,

 From http://grads.iges.org/grads/gadoc/script.html#intrinsic
---
read (filename)
This functions reads individual records from file filename. Repeated 
calls must be made to read consecutive records. The result is a string 
containing two lines: the first line is the return code, the 2nd line is 
the record read from the file. The record may be a maximum of 80 
characters. Use the sublin function to separate the result. Return codes 
are:

     0 - ok
     1 - open error
     2 - end of file
     8 - file open for write
     9 - I/O error

Files are opened when the first call to read is made for a particular 
file name. Files are closed when the execution of the script file 
terminates (note that files remain open between function calls, etc).
---

Try something like this in your script:
...
res = read(input)
rc = sublin(res,1)
if ( rc != 0 )
   say 'return code is: 'rc
   exit
endif
rec = sublin(res,2)
...

also, check on "looptime" vs "time" for loop counter...

Hope this helps,
Chuck


On 02/21/2013 01:03 PM, Phil Klotzbach wrote:
> Hi everyone,
>
> I am currently running GrADS 2.0.1 on my Windows 7 laptop.  What I have
> is a simple text file with three columns, a longitude, a latitude, and a
> time (since 1979 at 0Z).  When I attempt to run the code in GrADS, I get
> the following error message:
>
> Set error: Missing or invalid arguments for LON option
> Non-numeric args to numeric operations
> Error occurred on line 18
> In file /cygdrive/c/OPENGR~1/Contents/Resources/Scripts/readfile.gs
>
> The strange thing is, I can check and see that latitude has been set
> correctly by GrADS.  It just has problems with longitude and time. I
> used the three say commands to verify that it has read in the variables
> correctly (which it has).
>
> The following is my code as currently written:
>
> input = 'c:\test.txt'
> 'open c:\500mbtemp.ctl'
> looptime = 1
> while (looptime < 3)
> rec = read(input)
> pointlon = substr(rec, 2, 7)
> pointlat = substr(rec, 10, 7)
> pointtime = substr(rec, 17, 2)
> say pointlon
> say pointlat
> say pointtime
> 'set lat 'pointlat''
> 'set lon 'pointlon''
> 'set t 'pointtime''
> 'd temp'
> answer=result
> res=write("c:\500mbtemp.txt",answer)
> time=time+1
> endwhile
>
> Here are the contents of c:\test.txt
>
> 150.00 -16.75 5
> 149.25 -22.50 7
>
> Lastly c:\500mbtemp.ctl is an ERA-Interim 500 mb temperature file. I
> have verified manually that the file opened correctly and is working
> properly.   I know the GrADS treats all variables read from text files
> as strings, and I'm guessing that this is what is causing the problem
> here.  Any insights into how this problem can be solved are much
> appreciated!  Thanks!
>
> Phil
>

-- 

Please note that Charles.Seman at noaa.gov should be considered my NOAA
email address, not cjs at gfdl.noaa.gov.

********************************************************************
  Charles Seman                                Charles.Seman at noaa.gov
  U.S. Department of Commerce / NOAA / OAR
  Geophysical Fluid Dynamics Laboratory         voice: (609) 452-6547
  201 Forrestal Road                              fax: (609) 987-5063
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