NCL Home > Documentation > Functions > NCL object routines, Graphics routines

NhlRemoveOverlay

Removes one or more plots from an overlay.

Prototype

	procedure NhlRemoveOverlay (
		base_id [1] : graphic,  
		plot_id [*] : graphic,  
		restore [1] : logical   
	)

Arguments

base_id

A reference to an NCL plot that is the base of an overlay.

plot_id

An array of one or more plots to be removed from the base.

restore

A scalar logical value. If True and the member plot initially was a base plot of an overlay with its own members, the member plots are returned to the plot being removed.

Description

This procedure removes all of the elements of the plot_id array from the base_id plot and applies the restore value to each element. The restore parameter dictates how overlay elements that are themselves overlay bases handle their members. (See the HLU PlotManager description for more detail about overlays.)

See Also

NhlAddOverlay

Examples

Example 1

This example creates a map plot and overlays vectors and contours using NhlAddOverlay. It then uses NhlRemoveOverlay to remove the vectors and redraw the plot (for illustration only).

begin
  MSIZE = 73
  NSIZE = 73
  NROWS = 11

; 
; Define our own colormap.
;
  cmap = (/(/1.0,1.0,1.0/), \
           (/0.0,0.0,0.0/), \
           (/0.9,0.9,0.9/), \
           (/0.6,0.6,0.6/), \
           (/0.3,0.3,0.3/), \
           (/0.8,0.9,1.0/), \
           (/0.5,0.0,0.5/), \
           (/0.0,0.5,0.7/), \
           (/0.0,0.0,0.0/), \
           (/0.00000,1.00000,0.00000/), \
           (/0.14286,1.00000,0.00000/), \
           (/0.28571,1.00000,0.00000/), \
           (/0.42857,1.00000,0.00000/), \
           (/0.57143,1.00000,0.00000/), \
           (/0.71429,1.00000,0.00000/), \
           (/0.85714,1.00000,0.00000/), \
           (/1.00000,1.00000,0.00000/), \
           (/1.00000,0.85714,0.00000/), \
           (/1.00000,0.71429,0.00000/), \
           (/1.00000,0.57143,0.00000/), \
           (/1.00000,0.42857,0.00000/), \
           (/1.00000,0.28571,0.00000/), \
           (/1.00000,0.14286,0.00000/), \
           (/1.00000,0.00000,0.00000/) /)
;
; Create an ncgmWorkstation object.
;
  wks = create "vc07Work" xWorkstationClass defaultapp
    "wkColorMap" : cmap
  end create

;
; Read the data file.
;
;   data(0,:,:) is U
;   data(1,:,:) is V
;   data(2,:,:) is P
;
  path = ncargpath("examples")
  data = asciiread(path + "/fcover.dat",(/3,73,73/),"float")
  data@_FillValue = -9999.0
;
; Massage the data to eliminate surplus of vectors near the pole
;
  ithin = (/90,15,5,5,4,4,3,3,2,2,2/)
  do j=1,NROWS
    data(0,NSIZE-j,ind(ispan(1,MSIZE,1) % ithin(j-1) .ne. 0)) = -9999.0
  end do

;
; Create a MapPlot object.
; 
  map = create "mapplot" mapPlotClass wks
    "vpXF"                    : 0.05
    "vpYF"                    : 0.95
    "vpWidthF"                : 0.9
    "vpHeightF"               : 0.9

    "mpProjection"            : "Stereographic"
    "mpCenterLatF"            : 90.0
    "mpCenterLonF"            : 180.0
    "mpCenterRotF"            : 45.0
    "mpFillOn"                : True
    "mpGridAndLimbDrawOrder"  : "Draw"
    "mpGridLineDashPattern"   : 5
    "mpLabelsOn"              : False
    "mpLimitMode"             : "Corners"

    "mpLeftCornerLatF"        : 10.
    "mpLeftCornerLonF"        : -180.
    "mpRightCornerLatF"       : 10.
    "mpRightCornerLonF"       : 0.

    "mpLandFillColor"         : 3
    "mpOceanFillColor"        : 7
    "mpInlandWaterFillColor"  : 7
  end create

;
; Create a ScalarField object.
;
  sfield = create "ScalarField" scalarFieldClass defaultapp
    "sfDataArray"     : data(2,:,:)
    "sfMissingValueV" : data@_FillValue
    "sfXCStartV"      : -180.
    "sfYCStartV"      : -90.
    "sfXCEndV"        : 180.
    "sfYCEndV"        : 90.
  end create
;
; Create a VectorField object.
;
  vfield = create "VectorField" vectorFieldClass defaultapp
    "vfMissingUValueV" : -9999.0
    "vfMissingVValueV" : -9999.0

    "vfUDataArray"     : data(0,:,:)
    "vfVDataArray"     : data(1,:,:)
    "vfXCStartV"       : -180.
    "vfYCStartV"       :  -90.
    "vfXCEndV"         :  180.
    "vfYCEndV"         :   90.
  end create

;
; Create a VectorPlot object.
;
  vector = create "vectorplot" vectorPlotClass wks
    "vcUseScalarArray"         :  True
    "vcVectorFieldData"        :  vfield
    "vcScalarFieldData"        :  sfield
    "vcLevelSelectionMode"     : "ManualLevels"
    "vcMinLevelValF"           : 970.
    "vcMaxLevelValF"           : 1040.
    "vcLevelSpacingF"          : 5.
    "vcLevelColors"            : ispan(9,23,1)
    "vcLineArrowHeadMinSizeF"  :  0.007
    "vcLineArrowThicknessF"    : 3.0
    "vcMaxLevelCount"          : 15
    "vcMinFracLengthF"         : 0.4
    "vcMonoLineArrowColor"     : False
    "vcRefAnnoOn"              : False
    "vcRefLengthF"             : 0.054794524
  end create

  getvalues vector
    "vcMinMagnitudeF": vmin
    "vcMaxMagnitudeF": vmax
  end getvalues

  setvalues vector
    "vcMinMagnitudeF": vmin + 0.1 * (vmax - vmin)
  end setvalues

;
; Create a ContourPlot object.
;
  contour = create "contourplot" contourPlotClass wks
    "cnScalarFieldData"          : sfield
    "cnInfoLabelOn"              : False
    "cnLineColor"                : 6
    "cnLineLabelPerimOn"         : False
    "cnLineLabelsOn"             : False
    "cnLineThicknessF"           : 3.0
    "cnMaxLevelCount"            : 20
  end create

;
; Overlay the vectors and the contours on the map and draw
; everything.
;
  NhlAddOverlay(map,vector,map)
  NhlAddOverlay(map,contour,map)

  draw(map)
  frame(wks)

;
; Remove the vector overlay and redraw the plot.
;
  NhlRemoveOverlay(map,vector,False)
  draw(map)
  frame(wks)
end

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