Changing values in a .nc file

[Mark Schus]

Hi all,

I had asked this problem before, and someone sent me a solution, but this
was months ago, and now I have to do the same calculation again, but I
have forgotten how to.

I need to make a contour plot in grads for a region in NW Canada, but I
want to use my own values that are in a simple text file.  I don't know
how to read in values, but someone suggested that I create a 2D plot of
surface pressure from a .nc file, and then manually change all of the
values in that file to the ones that I would like to plot.

Can anyone tell me how to change point values?

For example, if I do

set lat 50
set lon 210
d pres

and the values is 101300 Pa, how can I change it so that it will be
something like 2.54?  Is it even possible?  I would like to manually
change every point so that I can have my own contour plot.  I can do this
in Excel, but then I won't have the nice topography background which grads
has.

Thanks for any help,

Mark