examples/graphs/integral.py

   1 from pyx import *
   2
   3 a, b = 2, 9 # integral area
   4
   5 p = graph.axispainter(basepathattrs=deco.earrow.normal(),
   6                       titlepos=0.98, titledirection=None)
   7 g = graph.graphxy(width=8, x2=None, y2=None,
   8                   x=graph.linaxis(title="$x$", min=0, max=10,
   9                                   part=[graph.tick(a, label="$a$"),
  10                                         graph.tick(b, label="$b$")],
  11                                   painter=p),
  12                   y=graph.linaxis(title="$y$",
  13                                   part=None, painter=p))
  14 style = g.plot(graph.function("y=(x-3)*(x-5)*(x-7)")).style
  15 g.finish()
  16
  17 pa = g.xgridpath(a)
  18 pb = g.xgridpath(b)
  19 (splita,), (splitpa,) = style.path.intersect(pa)
  20 (splitb,), (splitpb,) = style.path.intersect(pb)
  21 area = (pa.split(splitpa)[0] <<
  22         style.path.split(splita, splitb)[1] <<
  23         pb.split(splitpb)[0].reversed())
  24 area.append(path.closepath())
  25 g.stroke(area, deco.filled(color.gray(0.8)))
  26 g.text(g.pos(0.5 * (a + b), 0)[0], 1,
  27        r"\int_a^b f(x){\rm d}x", text.halign.center, text.mathmode)
  28 g.writetofile("integral")
  29