-5 5 setxrange
-1 1 setyrange
20 setxunit

traceOx

xticks
0 xtick
[-2 0 1 3] {xmark} apply

1.7 setlinewidth

gsave
0 4 translate
   orange
   [xmin 1] {0} apply
   (-]) ligne
grestore
gsave
0 -8 translate
   bleu
   [-3 2] {0} apply
   (]-[) ligne
grestore