折り曲げ模様のあるカオス

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program-id. chaos04.

data division.
working-storage section.
01 i pic 9(6).
01 a pic s9v999999.
01 b pic s9v999999.
01 x0 comp-2.
01 x1 comp-2.
01 y0 comp-2.
01 y1 comp-2.
01 ad pic x(20).

procedure division.
display 'Chaos04 Orimagemoyou' upon syserr
display 'a=' upon syserr no advancing accept ad compute a = function numval(ad)
display 'b=' upon syserr no advancing accept ad compute b = function numval(ad)
compute x0 = 0.1 compute y0 = 0
perform varying i from 1 by 1 until i > 50000
compute x1 = y0 + a * x0
compute y1 = x0 * x0 + b
display x1 ' ' y1
compute x0 = x1 compute y0 = y1
end-perform
exit program.

gnuplot -p -e "set title 'a=0.8 b=-0.8'; plot 'tmp' ps 0 lt rgb 'blue'"

gnuplot -p -e "set title 'a=0.4 b=-1.2'; plot 'tmp' ps 0 lt rgb 'red'"

gnuplot -p -e "set title 'a=-0.1 b=-1.7'; plot 'tmp' ps 0 lt rgb 'green'"

Default