The length of the path is determined by the number of points, Rod.
I agree that there should be a Save/Load preset functionality, I just don't know how to do it.
I agree that there should be a database somewhere of formulae with screenshots, maybe start a thread for that purpose here or something.
I think my formula viewer app is perfect for that - users will just play with it, then do PrintScreen when something nice has came out, then post it. The only draw back here is that formulas will have to be manually typed from the image by others.
TIP: During development I saved a few formulas inside the script comments. Check them out, they still there. Actually, I'll paste it here for convenience:
# loops vine
#X = i*4+sin(i*0.1)*100
#Y = 200+sin(i*0.05)*100*cos(i*0.1)
# loops sym
#X = i*2+(sin(i*0.05)*100)
#Y = 200+sin(i*0.05)*100*cos(i*0.1)
#loop chain border
#X = i*4+sin(i*0.1)*sin(i*0.2)*100
#Y = 200+sin(i*0.1)*cos(i*0.2)*100
#X = i*6+sin(i*1.618)*sin(i*1.618)*100
#Y = 200+cos(i*1.618)*sin(i*1.618)*80+sin(i*88)*200
#sin(i)*50+sin(i*1.1)*5+i*pi+sin(i)*1.2
#100+sin(i*1.1)*20+(sin(i)*20)
#((i*0.8)*4)+(sin(i*0.1)*phi)+(sin(i*0.8)*10)
#200+(sin(i*0.2)*20)*(sin(i*0.1)*phi)
#((i*0.4)*4)+(sin(i*0.4)*phi)+(sin(i*0.6)*10)-(sin(i*0.4)*20)
#100+(sin(i*0.2)*20)*(sin(i*0.2)*phi)
#nice loops
#((i*0.5)*5)+(sin(i*0.125)*100)
#100+(sin(i*0.25)*20)+(cos(i*1)*0.25)