On Tue, 7 Dec 2004, Yee Lau wrote:
> Hello,
>
> I have a huge dataset with random points of lon, lat and temperature values
> (500,000).
> I need to draw these on a map with the temperature being color-coded. I know
> how
> to create colormap and draw the points one by one using gsn_polymarker. I
> would like
> to know if there's any other way to draw the color-coded points using NCL
> which will
> speed up this process.
>
> Thanks for any info
> Yee
Hi Yee,
There is not really an easy way to do this in NCL. You can first
generate individual XY plots for each set of points that
you want to be represented by one color, and then overlay these on
a map. Below is an example where I've generated some dummy data
using "random_uniform", created two XY plots, one with red markers
and one with blue markers, and then I've overlaid both of these
on cylindrical equidistant map.
--Mary
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
begin
;
; Generate dummy data.
;
lat1 = random_uniform(-90.,90.,100)
lon1 = random_uniform(-180.,180.,100)
lat2 = random_uniform(-90.,90.,100)
lon2 = random_uniform(-180.,180.,100)
T = random_uniform(0.,80.,100)
wks = gsn_open_wks("x11","example")
res = True
res@gsnDraw = False
res@gsnFrame = False
map = gsn_csm_map(wks,res) ; Create a map; don't draw it yet.
res@xyMarker = 16
res@xyMarkLineMode = "Markers"
res@xyMarkerColor = "red"
xy1 = gsn_xy(wks,lon1,lat1,res) ; Create first XY plot.
res@xyMarkerColor = "blue"
xy2 = gsn_xy(wks,lon2,lat2,res) ; Create second XY plot.
overlay(map,xy1) ; Overlay both XY plots on map.
overlay(map,xy2)
draw(map) ; Draw map.
frame(wks) ; Advance frame.
end
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