Re: xy plot secondary axis

Hi Chad,

Dennis was looking at this late last week and he he tossed it to me today.

Take a look at tick mark example #6:
http://www.ncl.ucar.edu/Applications/tickmarks.shtml#ex6

It shows you how to label the right Y-axis differently than the left
Y-axis. Specifically, you need to set tmYUseLeft = False to tell NCL to
not use the left Y-axis labels ont he right.

I (+Dennis) have come up with an example on how to 1) allow NCL to
automatically draw Celsius labels on the right Y-axis at the same point
as the Y-left labels were drawn in Fahrenheit. This will likely produce
   Celsius labels that aren't nice looking, but it will be done
automatically. 2) Manually set up Celsius labels yourself, drawing nice
round Celsius labels independent of where the left hand Y=axis major
tick mark labels are. I would go with this method. I'm pretty sure I can
come up with a way to do this automatically, but I think it's likely you
will be happy with the manual method.

Both examples are drawn with the code below.
Good luck,
Adam (+Dennis)
;================================================================
load "$NCARG_ROOT/lib/ncarg/nclex/gsun/gsn_code.ncl"
load "$NCARG_ROOT/lib/ncarg/nclex/gsun/gsn_csm.ncl"

begin
   ntim = 9
   time = ispan(1,9,1)
   T = (/0.,0.71,1.,0.7,0.002,-0.71,-1.,-0.71,-0.003/)*50

   time_at_long_name = "time"
   T_at_long_name = "Temperature"
   T_at_units = "F"

   wks = gsn_open_wks("ps","test") ; Open an X11 workstation.

   res = True
   res_at_gsnDraw = False
   res_at_gsnFrame = False
   res_at_trYMinF = -60 ; in degrees F
   res_at_trYMaxF = 40. ; in degrees F
   plot = gsn_csm_xy(wks,time,T,res) ; Draw an XY plot

   getvalues plot
      "tmYLValues" : tmYLValues ; values used by NCL at major
tick marks
      "tmYRLabels" : tmYRLabels ; These are fahrenheit
   end getvalues
   degC = 0.55555555*(tmYLValues -32) ; convert F to C

   degC2 = round(degC*(10^2),0)/10^2

   setvalues plot
      "tmYUseLeft" : False
        "tmYRLabelsOn" : True
        "tmYRMode" : "Explicit"
        "tmYRValues" : tmYLValues
        "tmYRLabels" : degC2
   end setvalues
   draw(plot)
   frame(wks)
  ;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   res_at_gsnDraw = True ; draw plot 2 with nice Celsius labels
   res_at_gsnFrame = True
   res_at_tmYUseLeft = False
   res_at_tmYROn = True
   res_at_tmYRLabelsOn = True
   yleftlabels = ispan(-50,0,10)
   degF = (yleftlabels/0.555555)+32.
   res_at_tmYRMode = "Explicit"
   res_at_tmYRValues = degF
   res_at_tmYRLabels = yleftlabels

   plot2 = gsn_csm_xy(wks,time,T,res) ; Draw an XY plot
end

;========================================================================
load "$NCARG_ROOT/lib/ncarg/nclex/gsun/gsn_code.ncl"
load "$NCARG_ROOT/lib/ncarg/nclex/gsun/gsn_csm.ncl"

begin
   ntim = 9
   time = ispan(1,9,1)
   T = (/0.,0.71,1.,0.7,0.002,-0.71,-1.,-0.71,-0.003/)*50

   time_at_long_name = "time"
   T_at_long_name = "Temperature"
   T_at_units = "F"

   wks = gsn_open_wks("ps","test") ; Open an X11 workstation.

   res = True
   res_at_gsnFrame = False
   plot = gsn_csm_xy(wks,time,T,res) ; Draw an XY plot

   getvalues plot
      "tmYLValues" : tmYLValues ; values used by NCL at major
tick marks
      "tmYRLabels" : tmYRLabels ; These are fahrenheit
        "vpXF" : xstart
        "vpYF" : ystart
        "vpHeightF" : pheight
        "vpWidthF" : pwidth
   end getvalues
   degC = 0.555*(tmYLValues -32) ; convert F to C

   plot2 = create "plot" logLinPlotClass wks
      "tmYLOn" : False
        "tmXBOn" : False
        "tmXTOn" : False
        "tmYROn" : True
        "trYMaxF" : max(degC)
        "trYMinF" : min(degC)
        "pmTickMarkDisplayMode" : "Always"
        "tmYLBorderOn" : False
         "tmXTBorderOn" : False
         "tmXBBorderOn" : False
        "tmYRBorderOn" : True
        "vpXF" : xstart+0.08
        "vpWidthF" : pwidth
        "vpYF" : ystart
        "vpHeightF" : pheight
        "tmYLMode" : "Explicit"
        "tmYRLabelsOn" : True
        "tmYLValues" : degC
        "tmYLLabels" : degC
        "tmYRMajorLengthF" : 0.021
        "tmYRMajorOutwardLengthF" : 0.021
   end create
   draw(plot2)
   frame(wks)
end

Chad Bahrmann wrote:
> I am currently plotting temperature vs time using gsn_csm_xy in degrees
> F. I have been asked to make the secondary axis in degrees C but I have
> not been able to find any examples on how this is done. Can someone
> point me in the direction on how to accomplish this.
>
> Thanks in advance,
> Chad Bahrmann
> _______________________________________________
> ncl-talk mailing list
> ncl-talk_at_ucar.edu
> http://mailman.ucar.edu/mailman/listinfo/ncl-talk

-- 
--------------------------------------------------------------
Adam Phillips			             asphilli_at_ucar.edu
National Center for Atmospheric Research   tel: (303) 497-1726
ESSL/CGD/CAS                               fax: (303) 497-1333
P.O. Box 3000				
Boulder, CO 80307-3000	  http://www.cgd.ucar.edu/cas/asphilli
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