1 | initial version |

It seems that there is no implemented solution to the issue. No problem, there is a quick solution using bare hands. (Although we can plot the polygon by the `polygon`

command, there will be in the following a parallel plot of the edges...)

```
def plotLabelledPolygon( vertices, labels, space=0.1 ):
"""for two lists of same length,
of vertices in the real plane, A, B, C, ...
and of labels a, b, ... for AB, BC, ...
we associate a plot object consisting of the segments and the labels.
The labels are positioned corresponding to the middle of the segments,
there is some space left in between.
"""
p = plot( [] )
n = len( vertices )
if n < 3 or n != len( labels ):
return p
zVertices = []
for A in vertices:
if type(A) in ( tuple, list ): zA = A[0] + i*A[1]
elif A in CC : zA = A
else : zA = None # feel free to extend for vectors & Co...
zVertices.append( zA )
for ind in range(n):
j = ind+1 if ind+1 < n else 0
A, zA = vertices[ ind ], zVertices[ ind ]
B, zB = vertices[ j ], zVertices[ j ]
p += line( [ A, B ] )
zBA = zB - zA
if zBA == 0:
print "zA = %s and zB = %s coincide :: IGNORED" % ( zA, zB )
continue
zT = CC( zA + zBA / 2 - space * I * zBA / abs( zBA ) )
label = labels[ ind ]
p += text( '$%s$' % label, ( zT.real(), zT.imag() ) )
return p
```

Examples of usage:

```
vertices = [ (-1,0), (1,0), (0,1) ]
labels = [ 'a', 'b', 'c' ] # or simply abc
p = plotLabelledPolygon( vertices, labels )
p.axes_color( 'gray' )
p.show()
vertices = [ (0,0), (3,-3), (1,0), (3,3) ]
labels = 'abcd'
q = plotLabelledPolygon( vertices, labels, space=0.1 )
q.axes_color( 'gray' )
q.show()
```

(The font, the aspect, the axes, ... can be controlled in the plot object.)

Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.