A J script for drawing fractals from the julia set

julia_set.ijs

NB. A J script for drawing fractals from the julia set.
NB. Algorithm from:
NB. http://mathemartician.blogspot.com/2012/07/julia-set-in-julia.html

require 'viewmat'

S =: 100 NB. Detail level of image

NB. The iteration verb
julia =: 3 : 0 "0
 NB. Starting location
 c =. _0.8j0.156
 maxiter =. 256 NB. Max iteration level
 for_n. >:i.maxiter do.
  if. (|y) > 2 do.
   (n-1)
   return.
  end.
 y =. (y^2) + c
 end.
 maxiter
 return.
)

NB. Normalize
NB. Translate a set or two numbers into (_1 to 1)j(_1 to 1)
s =: S%2
cplx =: dyad : '((x-s)%s) j. ((y-s)%s)' "0

NB. The data matrix to be plotted
dat =: (>:i.S) cplx/ >:i.S

NB. Plot the matrix
viewmat |: julia (dat*1.55)

NB. Save the image as a PNG
NB. savemat_jviewmat_ 'full500.png'