Jeff, thanks for your reply.
One situation where one might require masked nearest neighbor interpolation is when, on a given fixed grid, interpolating velocities on cell corners (B-grid) to faces (C-grid). Cells will be defined as either land or ocean cells, masked or un-masked respectively. The masked or un-masked character of cells does not change. Interpolating velocities from corners adjacent to masked cells, to cell centers on un-masked cells will require the behavior in question. Imagine two adjacent cells, one masked and the other not. The velocities on the cell corners that lie on the coast (adjacent to a masked and an un-masked cell) are masked. A desireable behavior of the interpolator would be to produce an un-masked cell centered velocity on the un-masked cell that uses values from adjacent un-masked velocity values.
Juan: I can see why you want it in this case, but I think in general users would expect a masked value if the nearest neighbor is masked. In addition, I don't see how to implement it easily. How far are you willing to go to find a nearest neighbor that is not masked?
In short, for your use case you'll have to implement your own custom solution. Of course, if you can show me a simple modification to the Basemap interp function that does what you want, and can be enabled with a kwarg, I'll reconsider.
On 3/7/11 2:25 PM, Juan A. Saenz wrote:
On 8/03/11 12:23 AM, Jeff Whitaker wrote:
On 3/7/11 5:50 AM, Jeff Whitaker wrote:
On 3/6/11 8:58 PM, Juan A. Saenz wrote:
I use Basemap and netCDF4-python on a regular basis, and find them
very useful tools. Thank you for developing them!
I noticed that when using basemap.interp for nearest neighbor
(order=0) the interpolation is not masked, and nearest neighbor masked
values will be used in the interpolation. I was wondering if you could
suggest a way to do nearest neighbor interpolation where masked are
supported, i.e. nearest neighbor values that are not masked.
Thanks for your help,
Juan: I agree that this would be desirable behavior. Unfortunately,
it's not obvious to me how to do it. I'll think about it and get back
to you. (cc'ing matplotlib-users list).
Juan: On second thought, I'm not sure this is desirable behavior. I would guess that most of the time, if a nearest neighbor is masked, the user would expect the interpolation routine to return a masked value. I would be interested to hear what others think.
Jeffrey S. Whitaker Phone : (303)497-6313
Meteorologist FAX : (303)497-6449
NOAA/OAR/PSD R/PSD1 Email : Jeffrey.S.Whitaker@...259...
325 Broadway Office : Skaggs Research Cntr 1D-113
Boulder, CO, USA 80303-3328 Web : http://tinyurl.com/5telg