# set terminal pngcairo  transparent enhanced fontscale 1.0 size 600, 400 
# set output 'piecewise.3.png'
set border 16 front lt black linewidth 1.000 dashtype solid
set key at screen 0.5, 0.15 center center vertical Right noreverse enhanced autotitle nobox
set style data lines
set xyplane at 0
unset xtics
unset ytics
set title "Piecewise function of one parameter in 3D" 
set title  font ",15" textcolor lt -1 norotate
part1(x) = 0.5 + (9.*x-x**3)/ 24.
part2(x) = 1.0 + (x-3.0)**3 / 48.
NO_ANIMATION = 1
save_encoding = "utf8"
part1 = "part1: for x < 1  norm(x) ≈  ½ + (9x-x^3) / 24"
part2 = "part2: for x > 1  norm(x) ≈   1 +  (x-3)^3 / 48"
## Last datafile plotted: "+"
splot [-2:2][-2:2] sample    [h=1:5]   '+' using (cos(h)):(sin(h)):(h) lw 2,    [h=5:10]  '+' using (cos(h)):(sin(h)):(h) lw 4,    [h=10:15] '+' using (cos(h)):(sin(h)):(h) lw 2