Re: natgrid returns negative values

Hi Noel,

The default use of natgrid does allow for some interpolated values
beyond the range of your data. You can set control parameters using
nnsetp (http://www.ncl.ucar.edu/Document/Functions/Built-in/nnsetp.shtml)

Here's the list of parameters to control:
http://www.ncarg.ucar.edu//ngmath/natgrid/parameters.html

Look at parameters:
"non" for preventing negative values
"ext" for preventing extrapolation in the exterior of the grid

Take Care,

Bill Scheftic

On Mon, Feb 11, 2013 at 10:52 AM, Mary Haley <haley@ucar.edu> wrote:
> Hi Noel,
>
> Are you saying you think the negative values are wrong, or do you just want to get rid of them somehow? What do the 0 values represent in your data? That is, are they real values, or do they represent missing values?
>
> Could you provide us with a script and data so we can take a look?
>
> http://www.ncl.ucar.edu/report_bug.shtml#HowToFTP
>
> --Mary
>
> On Feb 11, 2013, at 10:34 AM, Noel Aloysius wrote:
>
>> Hi NCL,
>>
>> I am using natgrid to interpolate from a randomly-spaced (1600 points) grid to a regular-spaced rectilinear grid (47 x 47 lat/lon). I notice there are several negative values within the domain where it should all be positive. I mask out the region outside of the model domain. And the input data has no missing values but zeros are present.
>>
>> Is there are way or any other way to avoid negative values during the interpolation?
>>
>> Thanks,
>> Noel
>>
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Received on Mon Feb 11 11:22:39 2013