Filled Area By Height Plot
http://www.idlcoyote.com/gallery/height_filled_area_plot.pro
PRO Filled_Area_By_Height_Plot_FG, WINDOW=awindow
compile_opt strictarr
; Set up variables for the plot. Normally, these values would be
; passed into the program as positional and keyword parameters.
x = Findgen(101)
y = 4 * Sin(x * !DtoR) / Exp( (x-15) / 25.)
; Set up the low and high x indices of the area under the curve
; you want to fill.
low = 10
high = 45
; Find the y indices associated with the low and high indices.
lowY = 4 * Sin(low * !DtoR) / Exp( (low-15) / 25.)
highY = 4 * Sin(high * !DtoR) / Exp( (high-15) / 25.)
indices = Value_Locate(x, [low, high])
lowIndex = indices[0]
highIndex = indices[1]
; Make sure the indices you find correspond the the right X indices.
IF x[lowIndex] LT low THEN lowIndex = lowIndex + 1
IF x[highIndex] GT high THEN highIndex = highIndex - 1
; Open a window and return its reference to the user.
aWindow = Window(WINDOW_TITLE="Filled Area by Height Plot")
; Turn refresh off until we are finished adding all of the graphics
aWindow -> Refresh, /Disable
; Draw the plot axes.
fgPlot = Plot(x, y, /Current, XTitle='X Axis', YTitle='Y Axis', Color='Navy', $
Name='4*Sin(x) $\slash$ e^(x-15) $\slash$ 25')
;APPROACH 1
; - Use a bunch of polygons to fill the area under the curve. Necessary for
; versions of IDL < 8.2.1
IF (!Version.Release LE 8.2) THEN BEGIN
; Scale the y data for colors.
cgLoadCT, 4, /Brewer, Clip=[50, 230], RGB_Table=RGB_Table
; Draw the area under the curve with scaled colors.
min_y = Min(y[lowIndex:highIndex], Max=max_y)
colors = BytScl(y, MIN=min_y, MAX=max_y)
; Number of polygons to make
nPoly = highIndex-lowIndex
; Create the polygons
fgPolygons = objarr(nPoly)
FOR j=lowIndex,highIndex-1 DO BEGIN
;Each little area has to be its own color/polygon. Create the vertices.
xpoly = [x[j], x[j], x[j+1], x[j+1], x[j]]
ypoly = [!Y.CRange[0], y[j], y[j+1], !Y.CRange[0], !Y.CRange[0]]
;Create the polygon
fgPolygons[j-lowIndex] = Polygon(xpoly, ypoly, /Data, Target=fgPlot, $
LineStyle=6, /Fill_Background, $
Fill_Color=reform(RGB_Table[colors[j],*]), $
Name='Filled Area' + strtrim(j-lowIndex))
ENDFOR
;APPROACH 2
; - Use the Vert_Colors and RGB_Table keywords (introduced in IDL 8.2.1)
; - Cannot test because I have IDL 8.2
ENDIF ELSE BEGIN
; Create closed polygons to color fill.
yMin = fgPlot.YRange[0]
xpoly = [ low, low, x[lowIndex:highIndex], high, high]
ypoly = [yMin, lowY, y[lowIndex:highIndex], highY, yMin]
;Get the color table
cgLoadCT, 4, /Brewer, RGB_Table=RGB_Table
;Create an array of indices between 50 and 230, scaled by height.
; - The RGB_Table keyword in Polygon takes a full palette [256x3], so I
; presume giving a smaller palette will not work.
colors = BytScl(y, MIN=min_y, MAX=max_y, Top=256-76) + 50B
;Create a filled polygon and keep it in the data space.
; - I assume the Vert_Colors keyword will color the area between each
; vertice the correct color...
fgPoly = Polygon(xpoly, ypoly, /Data, Target=fgPlot, /Fill_Background, $
Fill_Color='Dodger Blue', Name='Area Under Plot', $
RGB_Table=RGB_Table, Vert_Color=colors, LineStyle=6)
ENDELSE
;Add lines at the edges of the filled region
yrange = fgPlot.YRange
fgLine1 = PolyLine([low, low], [yrange[0], lowY], /Data, Target=fgPlot, Color='Grey', $
Name='Low Line')
fgLine2 = PolyLine([high, high], [yrange[0], highY], /Data, Target=fgPlot, Color='Grey', $
Name='High Line')
; Bring the plot to the front
fgPlot -> Order, /Bring_To_Front
;Refresh the plot
aWindow -> Refresh
END ;*********************************************************** ******
; This main program shows how to call the program and produce
; various types of output.
; Display the plot in a resizeable graphics window.
Filled_Area_By_Height_Plot_FG, Window=window
; Create a PostScript file. Linestyles are not preserved in IDL 8.2.3 due
; to a bug. Only encapsulated PostScript files can be created.
window.save, 'filled_area_by_height_plot_fg.eps'
; Create a PNG file with a width of 600 pixels. Resolution of this
; PNG file is not very good.
window.save, 'filled_area_by_height_plot_fg.png', WIDTH=600
; For better resolution PNG files, make the PNG full-size, then resize it
; with ImageMagick. Requires ImageMagick to be installed.
window.save, 'filled_area_by_height_plot_fg_fullsize.png'
Spawn, 'convert filled_area_by_height_plot_fg_fullsize.png -resize 600 filled_area_by_height_plot_fg_resized.png'
END
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