!THIS PROGRAM MODELS A ROMEO AND JULIET "LOVE/HATE" ROMANCE.

!CHANGING THE PARAMETERS a,b,c,d in the DATA STATEMENT LETS

!YOU EXPLORE THE DYNAMICS OF DIFFERENT RELATIONSHIPS.

!YOU CAN ALSO CHANGE THE INITIAL VALUE OF R and J,

!WHICH IS THE SITUATION "AT FIRST SIGHT".

!

OPEN #1: SCREEN 0,1,0.5,1

SET WINDOW 0,1000,-10,10

!

OPEN #2: SCREEN 0,1,0.5,1

SET WINDOW 0,1000,-10,10

SET COLOR "RED"

PRINT "ROMEO'S LOVE"

SET COLOR "BLUE"

PRINT "JULIET'S LOVE"

SET COLOR "BLACK"

PLOT 0,-9.9;1000,-9.9

PLOT 0,0;1000,0

OPEN #3: SCREEN 0.25,.75,0,.5

SET WINDOW -10*1.33,10*1.33,-10,10

PLOT -10,-10;10,-10;10,10;-10,10;-10,-10

PLOT -10,0;10,0

PLOT 0,-10;0,10

PRINT

PRINT

PRINT "J vs.R"

!

!TRY DIFFERENT VALUES FOR a,b,c,d

READ a,b,c,d

DATA .1,-.1,.2,-.1

!DATA 0,0,.1,.1

!DATA .1,-.2,-.2,.1

!DATA add your own!

!

PRINT "a=";a

PRINT "b=";b

PRINT "c=";c

PRINT "d=";d

PLOT TEXT, AT 4,4: "LOVE-LOVE"

PLOT TEXT, AT -6,-6: "HATE-HATE"

LET R=4

LET J=4

!

Let t=0

LET dt=1

DO While t<1000

LET Rdot=a*R + b*J

LET Jdot=c*R + d*J

!

LET Rnew= R + Rdot*dt

LET Jnew= J + Jdot*dt

!

LET Rhalf=0.5*(Rnew+R)

LET Jhalf=0.5*(Jnew+J)

!

LET Rdot=a*Rhalf + b*Jhalf

LET Jdot=c*Rhalf + d*Jhalf

!

LET R= R + Rdot*dt

LET J= J + Jdot*dt

!

LET t= t+dt

!

WINDOW #1

SET COLOR "RED"

PLOT t,R;

!

WINDOW #2

SET COLOR "BLUE"

PLOT t,J;

!

WINDOW #3

SET COLOR "GREEN"

PLOT R,J;

!

LOOP

!

END

!

!