| Re: contour [message #10066 is a reply to message #8458] |
Fri, 03 October 1997 00:00   |
hcp
Messages: 41
Registered: August 1995
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Member |
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|> R. Bauer wrote:
|> > Who can explain me the cell_fill flag by contour.
[and Martin Schultz replied]
|> cell_fill splits the area to be filled into a number of smaller
|> cells (I think they are rectangles) instead of using some sophisticated
|> fill algorithm that uses the outline (contourline) of the area to be
|> filled. There are occasions when the standard fill produces very weird
|> results (I encountered these, but forgot how I made it), in these cases
|> cell_fill will be much more robust. It may be a good idea to try out
|> both algorithms (with and without cell_fill) if you have contour plots
|> with a lot of variety, many gaps in the data or other somewhat ill-posed
|> problems.
Also, be warned that in IDL 5.0 the cell_fill keyword does the same
as the fill keyword.
In IDL 5.0.2 /cell_fill is back but has bugs which occur on
map projections (one of the main places where you need cell_fill in
the first place). RSI are aware
of this. The workaround they suggest is to use this short program as
a wrapper around contour.
; ************************************************************ **
PRO CONTOUR_CELL, z, x, y, _EXTRA=e
; This program was supplied by RSI as a fix for the bigs in the
; cell_fill algorithm of the contour
; routine. contour_cell,data,xgrid,ygrid,/cell_fill will work where
; contour ,data,xgrid,ygrid,/cell_fill will not
nx = n_elements(x) ;Divide a rectangular grid into
;triangles
ny = n_elements(y)
tr = lonarr(6, nx-1, ny-1, /NOZERO)
for iy=0, ny-2 do for ix=0,nx-2 do $ ;Make the triangles
tr(0, ix, iy) = [0, 1, nx+1, 0, nx+1, nx] + (ix + iy*nx)
;2/cell
CONTOUR, z, x # replicate(1,ny), replicate(1,nx) # y, $
TRIANGULATION=tr, _EXTRA=e
end
; ************************************************************ **
Hugh
--
============================================================ ==============
Hugh C. Pumphrey | Telephone 0131-650-6026
Department of Meteorology | FAX 0131-662-4269
The University of Edinburgh | Replace 0131 with +44-131 if outside U.K.
EDINBURGH EH9 3JZ, Scotland | Email hcp@met.ed.ac.uk
OBDisclaimer: The views expressed herein are mine, not those of UofE.
============================================================ ==============
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