The following plots the Mandelbrot set (invented by IBM fellow
Benoit B. _) on an HP28S. The required positive integer saved as
BntB is the number of iterations that define a point as being in
the set. Theory requires _infinity_; I think the _Sci_Amer_ articles
used 1,000. I suggest 20->100; plots can take HOURS of continuous
computations, and new batteries will probably give you only a few
plots. Suggested CntrBBM starting coordinates nicely frame the
entire set. You then INS lower left & upper right corners to the
stack, ATTN, PMIN & PMAX, et al., and restart with _ALPHA_ _NEXT_
BntB Mndlbrt _ENTER_ or _new_param_ _NEXT_ Mndlbrt. PPAR is
automatically recomputed for the minimal 1:1 rectangle which frames
& centers your PMIN/PMAX inputs.
<< DUP TYPE 0 == << ABS IP 'BntB' STO PPAR 2 GET PPAR 1 GET - C->R
/ 137 32 / / DUP 1 >= << *H >> << INV *W >> IFTE << X PPAR 1 GET
IM PPAR 2 GET IM DUP2 SWAP - 31 / PPAR 4 GET * -> cR ym yM yi <<
ym yM FOR cI cR cI R->C (0,0) 0 -> c z n << DO n 1 + 'n' STO z SQ
c + 'z' STO UNTIL n BntB > z ABS 2 > OR END n BntB > << c PIXEL >>
IFT >> yi STEP >> PPAR 5 GET IM >> STEP CLLCD DRAW { EQ } PURGE {
PMIN PMAX RES CNTR *W *H BntB Mndlbrt } MENU DGTIZ >> IFT >>
'Mndlbrt' STO
<< { (-6.1015625,-1.25) (4.6015625,1.25) X 1 (9,9) } 'PPAR' STO >>
'CntrBBM' STO
* _ALPHA_ CntrBBM 25 Mndlbrt _ENTER_
* _INS_ for diagonal corners, _ATTN_, PMIN/PMAX/RES/CNTR/*W/*H
* _ALPHA_ BntB Mndlbrt _ENTER_ ---or,_e.g.--- 40 Mndlbrt
Question (I don't have the answer for this, but would like to know):
Given that the 28S's mantissa is twelve digits, batteries won't
support a BntB much bigger than 100, and letting CntrBBM be
"one-power", just HOW much magnification is reasonable? As the
math always computes differences from numbers around _1_, it would
seem reasonable that you can't go lower than 1E12 mag., but my
error analysis isn't that sound.... Feel free to use e-mail, or
even AT&T.
Glen Kilpatrick
(916)756-9321home