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MathGroup Archive 1992

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Plotting a polygon

  • To: mathgroup at yoda.physics.unc.edu
  • Subject: Plotting a polygon
  • From: koleh%joyl.dnet at joyx.joensuu.fi
  • Date: Fri, 11 Dec 1992 14:42:20 +0300

Hi Mathgroup !

What is the problem here? My student tried to plot a polygon in a
complicated way.

Mathematica 2.0 for MS-DOS 386/7
Copyright 1988-91 Wolfram Research, Inc.

In[1]:= t=Table[Random[],{5},{2}];

This works:

In[2]:= Show[Graphics[Map[Line,Partition[AppendTo[t,First[t]],2,1]]]]

Out[2]= -Graphics-

But when he uses a function polygon[], it does not work.

In[3]:= polygon[t_]:=
        Show[Graphics[Map[Line,Partition[AppendTo[t,First[t]],2,1]]]]

In[4]:= polygon[t]

AppendTo::rvalue: 
   {{0.10459, 0.840989}, {0.177361, 0.503785}, <<3>>, {0.10459, 0.840989}}
     has not been assigned a value.

AppendTo::argr: AppendTo called with 1 argument; 2 arguments are expected.

AppendTo::argr: AppendTo called with 1 argument; 2 arguments are expected.

Graphics::gprim: 
   Unknown Graphics primitive AppendTo[Line[AppendTo[<<2>>]]] encountered.

Out[4]= -Graphics-

In[5]:= ?polygon
Global`polygon

polygon[t_] := Show[Graphics[Line /@ Partition[AppendTo[t, First[t]], 2, 1]]]

Osmo Kolemainen
University of Joensuu
Finland 





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