Polar1.bas

companion program to the article
UNDERSTANDING AND PLOTTING POLAR COORDINATES by Tom Nally

 '***********************************************
 '
 'Polar1.bas by Nally + April 2000
 'Released as open source
 '
 'Polar1.bas plots the function defined
 'by R = 2.5 + 2*sin(12*phi) using polar
 'coordinates.
 '
 'To change the function plotted, locate
 'the branch label [Plot.click]. The
 'function is defined a few lines below
 'that branch label.
 '
 '***********************************************
 pi = 3.141592
 PlotType$ = "Markers"
 MarkerValue$ = "set"
 LineValue$ = "reset"
 Scalefactor = 1
 BiggestXY = 0
 xmin = 0
 xmax = 0
 ymin = 0
 ymax = 0
 Dim R(360)
 Dim x(360)
 Dim y(360)
 Dim xscaled(360)
 Dim yscaled(360)
 Dim xplot(360)
 Dim yplot(360)
 NoMainWin
 WindowWidth = 440
 WindowHeight = 265
 Graphicbox #main.PlotArea, 214, 21, 200, 200
 Button #main.Plot, "Plot !", [Plot.click], UL, 25, 126, 170, 30
 Groupbox #main.groupbox4, "Plot Appearance", 26, 16, 168, 105
 Radiobutton #main.radioMarkers, " Plot markers", [markers.Set], [markers.Set], 38, 46, 112, 20
 Radiobutton #main.radioLines, " Plot Lines", [Lines.Set], [Lines.Set], 38, 71, 96, 20
 Button #main.About, "About...", [About.click], UL, 30, 186, 74, 25
 Button #main.Quit, "Quit", [Quit.click], UL, 118, 186, 72, 25
 Open "Plotting Polar Coordinates" For Window As #main
 Print #main.PlotArea, "fill white; flush"
 Print #main, "font arial 10"
 Print #main, "trapclose [Quit.click]"
 GoSub [Print.Initial.Control.Values]
 [main.inputLoop] 'wait here for input event
 Wait
 GoTo [main.inputLoop]
 [Quit.click]
 Close #main: End
 [Print.Initial.Control.Values]
 Print #main.radioMarkers, "Set"
 Print #main.PlotArea, "fill white"
 Return
 [markers.Set]
 Print #main.radioMarkers, "value? MarkerValue$"
 If (MarkerValue$ = "set") Then
 PlotType$ = "Markers"
 End If
 If (MarkerValue$ = "reset") Then
 PlotType$ = "Lines"
 End If
 GoTo [main.inputLoop]
 [Lines.Set]
 Print #main.radioLines, "value? LineValue$"
 If (LineValue$ = "set") Then
 PlotType$ = "Lines"
 End If
 If (LineValue$ = "reset") Then
 PlotType$ = "Markers"
 End If
 GoTo [main.inputLoop]
 [Plot.click]
 'for all angles between zero and 360 degrees,
 'find the value of R as defined by
 'R = 2.5 + 2*sin(12*phi)
 For degree = 0 to 360
 phi = (degree/360) *(2*pi)
 R(degree) = 2.5 + 2*Sin(12*phi)
 Next degree
 'Convert polar coordinates to
 'cartesian coordinates
 For degree = 0 to 360
 phi = (degree/360) * (2*pi)
 x(degree) = R(degree) * Cos(phi)
 y(degree) = R(degree) * Sin(phi)
 Next degree
 'Find the extreme values of all cartesian
 'x and y values as a prelude to
 'finding the scalefactor
 xmax = 0
 xmin = 0
 ymax = 0
 ymin = 0
 For degree = 0 to 360
 If (x(degree) > xmax) Then xmax = x(degree)
 If (x(degree) < xmin) Then xmin = x(degree)
 If (y(degree) > ymax) Then ymax = y(degree)
 If (y(degree) < ymin) Then ymin = y(degree)
 Next degree
 BiggestXY = 0
 If (abs(xmax) > BiggestXY) Then BiggestXY = abs(xmax)
 If (abs(xmin) > BiggestXY) Then BiggestXY = abs(xmin)
 If (abs(ymax) > BiggestXY) Then BiggestXY = abs(ymax)
 If (abs(ymin) > BiggestXY) Then BiggestXY = abs(ymin)
 'Establish the scalefactor
 Scalefactor = 90 / BiggestXY
 'Create a scaled set of the cartesian coordinates
 'so that the data will plot nicely in the Graphicbox
 For degree = 0 to 360
 xscaled(degree) = Scalefactor * x(degree)
 yscaled(degree) = Scalefactor * y(degree)
 Next degree
 'Shift the data set to the center of the
 'Graphicbox, while also reversing the
 'direction of y.
 For degree = 0 to 360
 xplot(degree) = 100 + xscaled(degree)
 yplot(degree) = 100 - yscaled(degree)
 Next degree
 If (PlotType$ = "Lines") Then [Skip.To.Lines]
 'If markers have been selected, plot markers
 Print #main.PlotArea, "discard"
 Print #main.PlotArea, "cls"
 Print #main.PlotArea, "fill white"
 Print #main.PlotArea, "down"
 For degree = 0 to 360
 Print #main.PlotArea, "place " + Str$(xplot(degree)) + " " + Str$(yplot(degree))
 Print #main.PlotArea, "circle 2"
 Next degree
 GoTo [Plotting.Accomplished]
 [Skip.To.Lines]
 'If lines have been selected, plot lines
 Print #main.PlotArea, "discard"
 Print #main.PlotArea, "cls"
 Print #main.PlotArea, "fill white"
 Print #main.PlotArea, "down"
 For degree = 1 to 360
 xplot1 = xplot(degree - 1)
 yplot1 = yplot(degree - 1)
 xplot2 = xplot(degree)
 yplot2 = yplot(degree)
 Print #main.PlotArea, "line " + Str$(xplot1) + " " + Str$(yplot1) + " " + _
 Str$(xplot2) + " " + Str$(yplot2)
 Next degree
 [Plotting.Accomplished]
 Print #main.PlotArea, "flush"
 GoTo [main.inputLoop]
 [About.click]
 Notice "About Plotting Polar Coordinates" + Chr$(13) + _
 "By Nally + April 2000 " + Chr$(13) + _
 "Made with Liberty Basic " + Chr$(13) + _
 "Released as open source "
 GoTo [main.inputLoop]