load "hsv2rgb.ncl"
begin

;
; Open NetCDF file containing Geo-Potential height forecast
; information.
;
  filedir = ncargpath("data")
  filename = filedir + "/cdf/contour.cdf"
  cfile = addfile(filename,"r")

;
; Set the color map.
;
   ncolors = 13
   hue = fspan(0.,300.,ncolors)   ; Set hue range.
   sat = fspan(1.0,1.0,ncolors)     ; Set saturation range.
   val = fspan(0.8,0.8,ncolors)     ; Set value range.

   cmap  = new((/ncolors+2,3/),float)   ; Define (ncolors+2) x 3 float
                                        ; array to hold the color map.

   cmap(0,:)    = (/1.,1.,1./)   ; Set the background to white.
   cmap(1,:)    = (/0.,0.,0./)   ; Set the foreground to black.

   cmap(2:ncolors+1,:) = hsv2rgb(hue,sat,val) ; Generate smooth range of
                                              ; RGB values.

;
; Create an X workstation.
;
    wid = create "wks" xWorkstationClass defaultapp
      "wkColorMap" : cmap
    end create

  field = create "field" scalarFieldClass defaultapp
    "sfDataArray"     : cfile->Z(0,3,:,:) 
    "sfMissingValueV" : cfile->Z@_FillValue  ; Set missing value.
  end create

  xpos = (/0.12, 0.57, 0.12, 0.57/)   ; X and Y positions of
  ypos = (/0.95, 0.95, 0.53, 0.53/)   ; the four contour plots.

;
; Create a contour object.
;
  cnid = create "contour" contourPlotClass wid 
    "vpWidthF"             : 0.35
    "vpHeightF"            : 0.35
    "vpXF"                 : xpos(0)
    "vpYF"                 : ypos(0)

    "cnScalarFieldData"    : field

    "cnLevelSelectionMode" : "ManualLevels"  ; Manually select our 
    "cnMinLevelValF"       : 5400.0          ; own contour levels by
    "cnMaxLevelValF"       : 5950.0          ; specifying min, max,
    "cnLevelSpacingF"      :   50.0          ; and spacing.

    "cnFillOn"             : True            ; Turn on fill.
    "cnLineLabelsOn"       : False           ; Turn off line labels.
    "cnInfoLabelOn"        : False           ; Turn off info label.
    "cnLowLabelsOn"        : False           ; Turn off low label.
    "cnHighLabelsOn"       : False           ; Turn off high label.
  end create

  draw(cnid)  ; Draw contour plot.

;
; Loop through three more time steps and create and draw
; contour plots at each one.
;
  do i=1,3
    setvalues field
      "sfDataArray" : cfile->Z(i,3,:,:)   ; Select new time step.
    end setvalues

    setvalues cnid
      "vpXF"     : xpos(i)  ; Change X and Y positions
      "vpYF"     : ypos(i)  ; of the new contour plot.
    end setvalues

    draw(cnid)  ; Draw the new contour plot.
  end do

;
; Retrieve the contour levels and the colors used for filling the
; contours so we can use this information in a labelbar.
;
  getvalues cnid
    "cnLevels"     : levels
    "cnFillColors" : colors
  end getvalues

;
; Create a labelbar.
;
  lbid = create "labelbar" labelBarClass wid
    "vpXF"              : 0.25   ; Specify position of labelbar
    "vpYF"              : 0.13   ; in the viewport.
    "vpWidthF"          : 0.50
    "vpHeightF"         : 0.10

    "lbPerimOn"         : False               ; Turn off perimeter.
    "lbBoxCount"        : dimsizes(levels)+1  ; # of labelbar boxes.
    "lbOrientation"     : "Horizontal"        ; Default is vertical.
    "lbLabelAlignment"  : "InteriorEdges"     ; Default is "BoxCenters".
    "lbLabelStrings"    : levels              ; Labels for boxes.
    "lbFillColors"      : colors              ; Colors for boxes.
    "lbMonoFillPattern" : True                ; Fill them all solid.

  end create

  draw(lbid)  ; Draw the labelbar.
  frame(wid)  ; Advance the frame.
end