Question

I am trying to view a basic polygon read from a Shapefile using matplotlib and pyshp
But all my efforts yield just an empty axes with no polygon. Here are few of my tries, using the dataset showing the borders of Belgium:

import shapefile as sf
r = sf.Reader("BEL_adm/BEL_adm0")
p=r.shapes()
b=p[0]
points = b.points

import matplotlib.pyplot as plt
from matplotlib.path import Path
imporst matplotlib.patches as patches

verts = points

verts = []
for x,y in points:
    verts.append(tuple([x,y]))

codes = ['']*len(verts)
codes[0] = Path.MOVETO
codes[-1] = Path.CLOSEPOLY

for i in range(1,len(verts)):
    codes[i]=Path.LINETO

path = Path(verts, codes)
fig = plt.figure()
ax = fig.add_subplot(111)
patch = patches.PathPatch(path, facecolor='orange', lw=2)
ax.add_patch(patch)
ax.set_xlim(-2,2)
ax.set_ylim(-2,2)
plt.show()

Another try with patches also yields an empty frame:

fig = plt.figure(figsize=(11.7,8.3))

ax = plt.subplot(111)
x,y=zip(*b.points)
import matplotlib.patches as patches
import matplotlib.pyplot as plt
bol=patches.Polygon(b.points,True, transform=ax.transAxes)

ax.add_patch(bol)
ax.set_ylim(0,60)
ax.set_xlim(0,200)
plt.show()

Would be happy to see what I am missing.
Thanks, Oz

Answer 1

instead of calling set_xlim(), set_ylim() to set the range of axis, you can use ax.autoscale().

For your Polygon version, you don’t need to set transform argument to ax.transAxes, just call:

bol=patches.Polygon(b.points,True)