This is the second part of the Volterra Lotka formulas , in this instance we are selecting an initial condition and varying the parameters p & h across the plane. There's now another FreeBASIC file to obtain the sequences from the map generated by V-HeunPH.frm . The coordinates I used were : Top left corner . -2.0 1.5 Bottom right corner . 2 -1.5 ----------------------------------------------------------------------------------- comment{Volterra Lotka , p , h variable . V-HeunPH.frm initial condition [ x = 0.8 , y=0.8 ], this initial condition might be determined from the V-Heun map . [ p , h ] varied over plane . x' = x - x*y y' = -y + x*y } V-HeunPH { x=0.8 y=0.8 p=real(pixel) h=imag(pixel): u=x-x*y w=-y+x*y a=x+p*u b=y+p*w c=x+h*(u+(a-a*b)) d=y+h*(w+(-b+a*b)) x=c y=d z=x+flip(y) |z|