title: How to input a list of pairs of points in $R^2$ in sage corresponding to edges of a polygon, and to draw a picture of the corresponding polygon,?
body: <p>Suppose I want to input in Sage a set of pairs of points corresponding to the set of edges of a polygon. For example, say I want to generate a (non-convex) polygon in $R^2$ with the set (list) V of vertices:</p>
  
  <p>V= [[0,0], [1,0], [2,1], [2, -1]].</p>
  
  <p>and the set of edges</p>
  
  <p>E= [ [[0,0], [2,1]], [[2,1], [1,0]], [[2, -1], [1,0]], [[2, -1], [0,0]] ].</p>
  
  <p>I'm not sure how to input E into sage so that for example, [[0,0], [2,1]] is understood as the unique straight line segment joining [0,0] and [2,1].</p>
  
  <p>After that, I'd also like to generalize this to drawing a polyhedron in $R^3$ with the vertex set V, edge set E and the face set E.</p>