`help/posets/text/plot_poset` := TEXT(
`   `,
`FUNCTION:  plot_poset - plot posets (or acyclic directed graphs)`,
`    `,
`CALLING SEQUENCE:  plot_poset(P,<options>);`,
`                   plot_poset(P,X,<options>);`,
`                   plot_poset(P,n,<options>);`,
`    `,
`PARAMETERS:  P = a poset (or acyclic directed graph)`,
`             X = a set (the vertex set)`,
`             n = a positive integer (the number of vertices)`,
`     <options> = any of the following, in any order:`,
`           (1) ranked`,
`           (2) proportional`,
`           (3) stretch=<number>`,
`           (4) ecolor=<color>, or ecolor=<table>`,
`           (5) vcolor=<color> `,
`           (6) labels, or labels=<table> `,
`           (7) title=<string>`,
`   `,
`SYNOPSIS:   `,
`  plot_poset(P,X) plots the Hasse diagram of the poset P with vertex set X,`,
`  using Maple 2D graphics. The (default) embedding algorithm proceeds as`,
`  follows. First, the vertex set is arranged into "levels" according to`,
`  'filter'. The vertices within each level are then sorted by 'sort'. An`,
`  initial layout is then chosen, with equal horizontal spacing between the`,
`  vertices in each level. Finally, an adjustment algorithm is used to`,
`  horizontally shift the positions of vertices until there are no "phantom"`,
`  relations (i.e., vertices incident with the interior of an edge).`,
`   `,
`  plot_poset(P,n) does the same, if {1,...,n} is the vertex set of P.`,
`  plot_poset(P) does the same, provided that there are no isolated vertices.`,
`   `,
`  Note: 'plot_poset' requires Maple V Release 2, or later versions.`,
`   `,
`  There are several options for controlling the form of the plot:`,
`   `,
`  ranked   `,
`   Arrange the vertices into levels according to the procedure 'ranked', if`,
`   possible. If the poset is not ranked, then use 'filter' (the default).`,
`   `,
`  proportional`,
`   Use spacing between the vertices that is inversely proportional to the`,
`   number of vertices at that level. This tends to produce better-looking`,
`   plots for posets in which there are extreme variations in the number of`,
`   vertices in each level. `,
`   `,
`  stretch=<number>`,
`   Stretch the vertical axis by the indicated factor. In versions of Maple in`,
`   which plots appear in separate windows, similar effects can be achieved by`,
`   selecting Unconstrained from the Projection menu, and reshaping the window.`,
`   `,
`  ecolor=<color>`,
`   Specify the color of the edges in the plot. The default color is set by`,
`   the global variable ``posets/default``[ecolor], and is user-modifiable.`,
`   Initially, the default value for ecolor is red.`,
`   `,
`  ecolor=<table>`,
`   Specify individual colors for each (covering) edge of P. The entries of`,
`   the table should be subsets (of the covering edges) of P, and the index`,
`   corresponding to a given entry should be the desired color for the given`,
`   set of edges. Any edge of P not occurring in one of the color-sets will be`,
`   assigned the default edge color.`,
`   `,
`  vcolor=<color>`,
`   Specify the color of the vertices and labels (see below) in the plot. The`,
`   default color is set by the global variable  ``posets/default``[vcolor],`,
`   and is user-modifiable. Initially, the default value for vcolor is white.`,
`   `,
`  labels   `,
`   Specify that the vertices of P in the plot should be represented by their`,
`   names, rather than by points (the default).`,
`   `,
`  labels=<table>`,
`   Specify a special label for each vertex of P. The indices of the table`,
`   should be the vertices of P, and corresponding entries are the desired`,
`   labels. The table entries must be of type 'string' (not names or numbers).`,
`   `,
`  title=<string>`,
`   Print the indicated title.`,
`    `,
`EXAMPLES:   `,
`  P:=J({},4);`,
`  plot_poset(P,title=``Boolean Algebra on 4 Points``);`,
`  Q:=subinterval(P,[1,12]);`,
`  C:=table([green=Q]);`,
`  plot_poset(P,ecolor=C,labels);`,
`  P:={[1,2],[2,3],[4,3],[4,5],[5,6]};`,
`  plot_poset(P,ranked,labels,vcolor=green);`,
`  P:=({},1) &+ rand_poset(20,0.3);`,
`  plot_poset(P,stretch=1.5);`,
`  M:=mobius(P):`,
`  L:=table([seq(i=convert(M[1,i],'string'),i=1..21)]);`,
`  plot_poset(P,labels=L);`,
`  P:=({},1) &+ ({},2) &+ ({},10) &+ ({},2) &+ ({},1);`,
`  plot_poset(P,proportional);`,
`    `,
`SEE ALSO: colors, filter, ranked`
):
save `help/posets/text/plot_poset`, ``.HomeLib.`/help/posets/text/plot_poset.m`;
quit