[Edu-sig] thought re graphing calculators ...

[Gregor Lingl]

kirby urner schrieb:
>> Hi Brian,
>>
>> ....
> This ran perfectly on Python 3.1rc1 (r31rc1:73069, May 31 2009,
> 08:57:10) on my WinXP box (one of a few).
>
> Note:  if this level of chaos / noise bothers you (the functions are
> algebraically the same, after all), then I recommend using the decimal
> type instead of the floating type, converting to float just to make
> your turtle happy:
>   
That's fine (for the turtle). But if someone thinks that everything is 
calculated
"correctly" now, she/he is bound to get disappointed. And that's the 
point (imho).

Regards,
Gregor


# Author: Gregor Lingl
# amended to use Decimal by Kirby Urner 2009-09-28
# re-corrupted to show the vainness (in principle) of kirby's effort 
2009-09-28
# Date: 2009-06-24

# A demonstration of chaos

from turtle import *
from decimal import Decimal

k = Decimal('3.9')

N = 160

def f(x):
 x = Decimal(str(x))
 return k*x*(1-x)

def g(x):
 x = Decimal(str(x))
 return k*(x-x**2)

def h(x):
 x = Decimal(str(x))
 return k*x-k*x*x

def jumpto(x, y):
 penup(); goto(x,y)

def line(x1, y1, x2, y2):
 jumpto(x1, y1)
 pendown()
 goto(x2, y2)

def coosys():
 line(-1, 0, N+1, 0)
 line(0, -0.1, 0, 1.1)

def plot(fun, start, colour):
 pencolor(colour)
 x = start
 jumpto(0, x)
 pendown()
 dot(5)
 for i in range(N):
     x=fun(x)
     goto(i+1,float(x))
     dot(5)

def main():
 reset()
 setworldcoordinates(-1.0,-0.1, N+1, 1.1)
 speed(0)
 hideturtle()
 coosys()
 plot(f, 0.35, "blue")
 plot(g, 0.35, "green")
 plot(h, 0.35, "red")
 # Now zoom in:
 for s in range(220):
     setworldcoordinates(0.5*s,-0.1, N+1, 1.1)
 return "Done!"

if __name__ == "__main__":
 main()
 mainloop()