Thank you very much for your kind help. I can now plot things the way I need
to! For your information, we are currently moving away from PV-WAVE to NCAR
graphics / NCL ... :)
page AT sca.uqam.ca http://meteocentre.com/
Agent de recherche et de planification +1 514 987 3000 ext. 2376
Departement des Sciences de la Terre et de l'Atmosphere UQAM
On Tue, 5 Feb 2002, Mary Haley wrote:
> > Hi,
> > Is there a way in NCL to overlay two 2D fields in a contour plot (let's say
> > the 1st field in solid lines and the second in dashed lines) and have a
> > legend at the top showing 2 items, one for each field?
> > All I could get is a legend showing all the line levels of the fields.
> > Thanks,
> > Christian Page
> > page AT sca.uqam.ca http://meteocentre.com/
> There are a couple of ways you can do this, and I'll give you an
> example of one of them. I wrote a little procedure that creates and
> draws a legend (gsn_legend_ndc), and added it to gsn_code.ncl, so you
> will need to download the latest version of gsn_code.ncl (more on this
> in a bit).
> The example below is uses data that is all on the same lat/lon grid,
> so by using coordinate arrays provided in the netCDF file, it knows
> how to do the overlay properly. (This is all done behind the scenes in
> the gsn_csm_contour routine.)
> This example basically creates two separate contour plots, overlays
> one on the other, draws the overlaid plots, and then draws a legend on
> If you want to draw the legend *inside* the plot area, then you can do
> all of this by using gsn_add_polyline and gsn_add_text. This will then
> allow you to panel the plots.
> To run the example below, first download the latest gsn_code.ncl
> and gsn_csm.ncl from:
> Here's the example:
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
> diri = "$NCARG_ROOT/lib/ncarg/data/cdf/" ; directory
> fili = "contour.cdf" ; file name
> f = addfile (diri+fili , "r") ; add file
> T1 = f->T(0,0,:,:) ; get 1st time and level
> T5 = f->T(4,0,:,:) ; get 5th time and level
> wks = gsn_open_wks ("x11", "legend" ) ; open workstation
> res = True
> res@vpYF = 0.85
> res@gsnDraw = False
> res@gsnFrame = False
> res@cnLineColor = "Red" ; red contour lines
> res@cnLineDashPattern = 0 ; solid lines
> plot1 = gsn_csm_contour(wks, T1, res )
> res@cnLineColor = "Blue" ; blue contour lines
> res@cnLineDashPattern = 12 ; dashed lines
> res@cnLineThicknessF = 2.
> res@gsnRightString = ""
> res@gsnLeftString = ""
> res@gsnCenterString = ""
> plot5 = gsn_csm_contour(wks, T5, res )
> overlay(plot1,plot5) ; Overlay plots; plot1 now
> ; contains the overlaid plot5.
> draw(plot1) ; Draw base plot.
> ; Set some legend resources.
> lgres = True
> lgres@lgLineColors = (/"red","blue"/) ; line colors for legend lines
> lgres@vpWidthF = 0.8 ; width of legend (NDC)
> lgres@vpHeightF = 0.1 ; height of legend (NDC)
> lgres@lgPerimOn = False ; turn off perimeter
> lgres@lgDashIndexes = (/0,12/) ; dash indexes
> lgres@lgLineLabelStrings = (/"",""/) ; no labels in lines
> ; Draw the legend, indicating the number of items, a label for each
> ; item, and the X, Y position of the legend in NDC coordinates.
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