[ncl-talk] how does interpolation work in contour plot?

[Will Hobbs]

Hi Lesley

Sorry, can’t point you to a detailed explanation, but the default contouring mode is ‘AreaFill’, and there is a bit of a description under the ‘cnFillMode’ resource help entry.

Have you tried setting cnFillMode = “RasterFill”, with the same explicit levels? I suspect it will ‘digitise’ the filling in the way that you want (but I don’t know).

Will

From: ncl-talk <ncl-talk-bounces at ucar.edu> on behalf of Lesley Smith - NOAA Affiliate via ncl-talk <ncl-talk at ucar.edu>
Reply-To: Lesley Smith - NOAA Affiliate <lesley.l.smith at noaa.gov>
Date: Friday, 1 November 2019 at 11:49 AM
To: ncl-talk <ncl-talk at ucar.edu>
Subject: [ncl-talk] how does interpolation work in contour plot?

Hi ncl-talk,
I'm trying to plot the season of the year with maximum precipitation
for each grid-point in the U.S.
I created a matrix of output, dimensioned lat x lon.
There are only 4 possible (integer)values: 1,2,3,4 <--which I checked.
(1 is DJF, 2 is MAM, etc. I'll make this pretty later.)
I get the attached plot, cam1x1_maxx_doy_precip.r01.1901.jpg,
(which I hope you can see) which I believe is correct.
However, I do not understand why there appear to be so many floats
in the plot. Is there some kind of interpolation going on?
When I try to set the contour levels explicitly, 1,2,3,4 I do
not seem to get a correct result.
Thus, it would be awesome if someone could point me to
a page explaining interpolation in contour plots.
Thanks very much!
-Lesley Smith


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