newgraph
border

(* Both axes should have same scale and size, and scale must be symmetric.
   In other words, choose the most extreme number seen in max(r_j-r_f),
   min(r_j-r_f), max(r_M-r_f), min(r_M-r_f) *)
xaxis
   size 3
   min -35 max 35
   draw_at 0
   draw_hash_marks_at -35
   draw_hash_labels_at -36

yaxis
   size 3
   min -35 max 35
   draw_at 0
   draw_hash_marks_at -35
   draw_hash_labels_at -36

newcurve
   linetype none
   marktype circle marksize 0.7
   pts include 9.dat

newcurve
   linetype solid
   marktype none
   linethickness 2.0
   pts
      shell : gawk 'BEGIN {printf("%f %f\n", -35, 0.656+(-35*0.86)); printf("%f %f\n", +35, 0.656+(+35*0.86))}'

newstring x -5 y 30 : r_j - r_f
newstring x -30 y 2 : r_M - r_f