creating contour plots with .txt data

[Stephen R McMillan]

Mark,
Regarding 1st item below...if the number of columns (probably longitude)
produces lines of text greater than the GrADS read-text limit, then I
recommend arranging the text such that each line contains the information
for only one grid value. Script-wise, may be easier that way regardless.
For example:

-97.5  40  1015
 -95  40  1013.2
-92.5  40  1018.7
etc.

Steve Mc






Stephen R. McMillan/Planalytics
10/05/2005 09:57 AM

To
GRADSUSR at LIST.CINECA.IT
cc

Subject
Re: creating contour plots with .txt data





Mark,
Yes you can, and I do this routinely. Something similar to the following:

1. Save your data in a space or tab delimited text format, with the data
arranged in the desired grid format.
2. Open a control file corresponding to the desired output resolution and
projection. For example, you could "sdfopen" an existing sea level
pressure file having the 2.5x2.5 resolution you mentioned.
3.Set your output resolution (set lat, lon, etc.), and time to a single
value.
3. Define a "template" variable. For example, 'define
tempvar=const(slp,1013,-a)' to set up a "blank" 1013 slp field.
4. Read in your data one grid value at a time, convert the corresponding
coordinates to grid coordinates ('q w2gr'), then use the "set defval"
command to modify the corresponding grid value to your input variable's
value.
5. Plot and contour your new data field.

Hope this works for you. Not knowing your GrADS experience level, the
above is pretty general. Holler for further assistance.

Steve Mc




Mark Schuster <m_schus at YORKU.CA>
Sent by: GRADSUSR at LIST.CINECA.IT
10/05/2005 03:43 AM
Please respond to
GRADSUSR at LIST.CINECA.IT


To
GRADSUSR at LIST.CINECA.IT
cc

Subject
creating contour plots with .txt data





Hi

I was wondering if anybody knows if I could use grads to make a contour
plot of
variables that i have in a regular text file.  A have average moisture
flux
values for specific lat/lon squares and would like to create a contour
plot of
these. I have tried doing this with Excel, but Excel creates the stupidest
looking plot, and my values are averages over a 2.5x2.5 degree square, and
Excel is interpreting them as being point values.

Can anyone suggest anything?

Thanks a lot

Mark

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