# set terminal svg size 600,400 dynamic enhanced fname 'arial'  fsize 10 mousing name "piecewise_2" butt dashed dashlength 1.0 
# set output 'piecewise.2.svg'
set format x "%.1f"
set format y "%.1f"
set format x2 "%.1f"
set format y2 "%.1f"
set format z "%.1f"
set format cb "%.1f"
set format r "%.1f"
set key inside left top vertical Left reverse enhanced autotitles nobox
set key invert samplen 4 spacing 1 width 0 height 0 
set label 1 "plot norm(x),  [0:1] part1(x),  [1:4] part2(x)" at 1, 0.62, 0 left norotate back nopoint offset character 0, 0, 0
set arrow 1 from 1, 0.7, 0 to 1, 0.9, 0 nohead back nofilled linetype -1 linewidth 1.000
set style line 1  linetype 0 linewidth 3.000 pointtype 0 pointsize default pointinterval 0
set style line 2  linetype 0 linecolor rgb "red"  linewidth 3.000 pointtype 0 pointsize default pointinterval 0
set style data lines
set xtics border in scale 1,0.5 nomirror norotate  offset character 0, 0, 0 autojustify
set title "Piecewise approximation to the\nNormal Cumulative Distribution Function" 
set xrange [ 0.00000 : 4.00000 ] noreverse nowriteback
set yrange [ 0.500000 : 1.10000 ] noreverse nowriteback
part1(x) = 0.5 + (9.*x-x**3)/ 24.
part2(x) = 1.0 + (x-3.0)**3 / 48.
save_encoding = "utf8"
GPFUN_part1 = "part1(x) = 0.5 + (9.*x-x**3)/ 24."
GPFUN_part2 = "part2(x) = 1.0 + (x-3.0)**3 / 48."
part1 = "part1: for x < 1  norm(x) ≈  ½ + (9x-x^3) / 24"
part2 = "part2: for x > 1  norm(x) ≈   1 +  (x-3)^3 / 48"
plot norm(x) lt -1,      [1:4] part2(x) ls 2 title part2,      [0:1] part1(x) ls 1 title part1