design/selfinter2.py

   1 #!/usr/bin/env python3
   2 import sys;sys.path.insert(0, "..")
   3 from math import *
   4 from pyx import *
   5 # File for invalid parametrisations of Bezier curves
   6 # Draws a sketch of the areas where invalid params are to be expected
   7
   8 xmin, xmax = -2, 5
   9 ymin, ymax = -xmax, 2
  10
  11 g = graph.graphxy(width=10,
  12     x=graph.axis.lin(title=r"$\Delta x$", min=xmin, max=xmax),
  13     y=graph.axis.lin(title=r"$\Delta y$", min=ymin, max=ymax),
  14     key=graph.key.key(pos="tr"),
  15 )
  16 g.plot(graph.data.function("y(x)=-1", title=None), [graph.style.line([style.linestyle.dotted])])
  17 d1 = g.plot(graph.data.function("x(y)=(-1-2*y-sqrt((1+2*y)**2+3))/3.0", title=r"cusp ($-$)"), [graph.style.line()])
  18 d2 = g.plot(graph.data.function("x(y)=(-1-2*y+sqrt((1+2*y)**2+3))/3.0", title=r"cusp ($+$)", max=-1), [graph.style.line([color.rgb.red])])
  19 d3 = g.plot(graph.data.function("x(y)=1.0/(3.0*(y+1))", title=r"passes through $(0,0)$", max=-1), [graph.style.line([color.rgb.green])])
  20 d4 = g.plot(graph.data.function("x(y)=(1+y**3)/(3.0*(1+y))", title=r"passes through $(1,0)$", max=-1), [graph.style.line([color.rgb.blue])])
  21 g.doplot()
  22
  23 p = d1.path << d3.path.reversed()
  24 p.append(path.closepath())
  25 g.layers["filldata"].fill(p, [color.gray(0.8)])
  26
  27 p = d2.path << d4.path.reversed()
  28 p.append(path.closepath())
  29 g.layers["filldata"].fill(p, [color.gray(0.8)])
  30
  31 g.writePDFfile()
  32
  33
  34