Polar Plotter-Example (1)

This program plots polar functions of the form

radius = f(angle)

Program settings are made for iPad. To run on iPhone/iPod Touch change:

W = 320

H = 460

U = 20

change line 160 to plot other polar functions

160 DEF FN F(T) = 5

160 DEF FN F(T) = T / (2 * PI)

160 DEF FN F(T) = 5 * SIN(4 * T)

160 DEF FN F(T) = 4 * SIN(6 * T) + 4

to understand math behind polar plotting I recommened Wikipedia: Go Wiki

full program:

10 REM POLAR PLOT PROGRAM

20 REM INIT

30 SCREEN 1

40 W = 768

50 H = 1024-20

60 U = 40

70 XC = W / 2

80 YC = H / 2

90 DEF FN MX(X) = XC + X * U

100 DEF FN MY(Y) = YC - Y * U

110 S = 1 / U

120 PI = 3.1415926

130 REM DRAW AXIS

140 GOSUB 1000

150 REM SET PARAMETERS

160 DEF FN F(T) = 5*SIN(6*T)-1

170 C = 3

180 TS = 0

190 TF = 2 * PI

200 GPRINT "r = 5 sin(6 theta)-1", 10, 80, C

210 REM PLOT

220 GOSUB 2000

230 SLEEP 15000

240 END

1000 REM [DRAW AXIS]

1010 CLS

1020 N = INT(XC / U)

1030 FOR I = 1 TO N

1040 CIRCLE XC, YC, I * U, 15, 0

1050 NEXT I

1060 LINE XC, 0, XC, H, 1

1070 LINE 0, YC, W, YC, 1

1080 RETURN

2000 REM [PLOT]

2010 T = TS

2020 R = FN F(T)

2030 X = R * COS(T)

2040 Y = R * SIN(T)

2050 XX = FN MX(X)

2060 IF XX < 0 THEN XX = 0

2070 YY = FN MY(Y)

2080 IF YY < 0 THEN YY = 0

2090 MOVETO XX, YY

2100 T = T + S

2110 R = FN F(T)

2120 X = R * COS(T)

2130 Y = R * SIN(T)

2140 XX = FN MX(X)

2150 IF XX < 0 THEN XX = 0

2160 YY = FN MY(Y)

2170 IF YY < 0 THEN YY = 0

2180 LINETO XX, YY, C

2190 IF T <= TF THEN 2100

2200 FRAME 0, 0, W-1, H-1, 0

2210 RETURN