Re: Avoiding extrapolation with shgrid

John,

I have heard back from Professor Renka on this. He says that the
Fortran code
that shgrid is based on does not calculate a convex hull. As to
cssgrid, it does
calculate a convex hull and there is a flag set by one of the lower
level
interpolation functions that indicates if a value is an extrapolated
value. That
subroutine is CSINTRC0. It would be some time before we could provide
NCL functionality that will do what you want, but if you are
interested you could
download the Fortran source for cssgrid from:

   http://ncarg.ucar.edu/ng4.4/download.html

and experiment with mods to the Fortran and wrap the modified code as
described at:

   http://www.ncl.ucar.edu/Document/Manuals/Ref_Manual/NclExtend.shtml

Regards,

Fred Clare

On Sep 17, 2007, at 4:41 AM, John Weissberg wrote:

> I am using shgrid but I very much want to avoid using it outside of
> the convex hull of my measurement points.
>
> Certain other interpolation functions in the library contain
> control parameters to enable/disable extrapolation.
>
> Is there a way to prevent extrapolation with shgrid or cssgrid?
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Received on Fri Sep 21 2007 - 14:28:12 MDT