set term svg font "Arial,20" size 1024,600
set out "Cspline.svg"
set multiplot layout 2,2 title "cspline, derivative, integral"
set key top right
set xtics 1
set grid
set rmargin 0
plot [][-1:1]\
 "out.txt" index 0 with points pointtype 7 title "points"\
,"out.txt" index 1 u 1:2 with lines title "exact"\
,"out.txt" index 1 u 1:3 with lines title "cspline"
set key center top
set ytics format ""
set rmargin
plot [][-1:1]\
 "out.txt" index 2 u 1:2 with lines title "exact derivative"\
,"out.txt" index 2 u 1:3 with lines title "spline derivative"
set ytics format "%h"
set key center bottom
set rmargin 0
plot [][0:2]\
 "out.txt" index 3 u 1:2 with lines title "exact integral"\
,"out.txt" index 3 u 1:3 with lines title "spline integral"
unset multiplot