@Section
   @Title { Adding a key to the graph }
   @Tag { key }
@Begin
@PP
A @I key to a graph is an explanation of what each data set
graphs. @RawIndex { graphs (statistical) }
graphs.keys @SubIndex { keys }
keys.graph @Index { keys in graphs }
represents.  To assist you in constructing a key, some extra symbols
are provided in addition to {@Code "@Graph"}:
graphs. @RawIndex { graphs (statistical) }
graphs.graphcross @SubIndex { @Code "@GraphCross" symbol }
{ graphacross } @Index { @Code "@GraphCross" symbol (graphs) }

graphs. @RawIndex { graphs (statistical) }
graphs.graphplus @SubIndex { @Code "@GraphPlus" symbol }
{ graphaplus } @Index { @Code "@GraphPlus" symbol (graphs) }

graphs. @RawIndex { graphs (statistical) }
graphs.graphsquare @SubIndex { @Code "@GraphSquare" symbol }
{ graphasquare } @Index { @Code "@GraphSquare" symbol (graphs) }

graphs. @RawIndex { graphs (statistical) }
graphs.graphfilled.square @SubIndex { @Code "@GraphFilledSquare" symbol }
{ graphafilled.square } @Index { @Code "@GraphFilledSquare" symbol (graphs) }

graphs. @RawIndex { graphs (statistical) }
graphs.graphdiamond @SubIndex { @Code "@GraphDiamond" symbol }
{ graphadiamond } @Index { @Code "@GraphDiamond" symbol (graphs) }

graphs. @RawIndex { graphs (statistical) }
graphs.graphfilled.diamond @SubIndex { @Code "@GraphFilledDiamond" symbol }
{ graphafilled.diamond } @Index { @Code "@GraphFilledDiamond" symbol (graphs) }

graphs. @RawIndex { graphs (statistical) }
graphs.graphcircle @SubIndex { @Code "@GraphCircle" symbol }
{ graphacircle } @Index { @Code "@GraphCircle" symbol (graphs) }

graphs. @RawIndex { graphs (statistical) }
graphs.graphfilled.circle @SubIndex { @Code "@GraphFilledCircle" symbol }
{ graphafilled.circle } @Index { @Code "@GraphFilledCircle" symbol (graphs) }

graphs. @RawIndex { graphs (statistical) }
graphs.graphtriangle @SubIndex { @Code "@GraphTriangle" symbol }
{ graphatriangle } @Index { @Code "@GraphTriangle" symbol (graphs) }

graphs. @RawIndex { graphs (statistical) }
graphs.graphfilled.triangle @SubIndex { @Code "@GraphFilledTriangle" symbol }
{ graphafilled.triangle } @Index { @Code "@GraphFilledTriangle" symbol (graphs) }

graphs. @RawIndex { graphs (statistical) }
graphs.graphnoline @SubIndex { @Code "@GraphNoLine" symbol }
{ graphanoline } @Index { @Code "@GraphNoLine" symbol (graphs) }

graphs. @RawIndex { graphs (statistical) }
graphs.graphsolid @SubIndex { @Code "@GraphSolid" symbol }
{ graphasolid } @Index { @Code "@GraphSolid" symbol (graphs) }

graphs. @RawIndex { graphs (statistical) }
graphs.graphdashed @SubIndex { @Code "@GraphDashed" symbol }
{ graphadashed } @Index { @Code "@GraphDashed" symbol (graphs) }

graphs. @RawIndex { graphs (statistical) }
graphs.graphdotted @SubIndex { @Code "@GraphDotted" symbol }
{ graphadotted } @Index { @Code "@GraphDotted" symbol (graphs) }

graphs. @RawIndex { graphs (statistical) }
graphs.graphdotdashed @SubIndex { @Code "@GraphDotDashed" symbol }
{ graphadotdashed } @Index { @Code "@GraphDotDashed" symbol (graphs) }

graphs. @RawIndex { graphs (statistical) }
graphs.graphdotdotdashed @SubIndex { @Code "@GraphDotDotDashed" symbol }
{ graphadotdotdashed } @Index { @Code "@GraphDotDotDashed" symbol (graphs) }

graphs. @RawIndex { graphs (statistical) }
graphs.graphdotdotdotdashed @SubIndex { @Code "@GraphDotDotDotDashed" symbol }
{ graphadotdotdotdashed } @Index { @Code "@GraphDotDotDotDashed" symbol (graphs) }

@ID @Tab
    @Fmta { @Col @Code A ! @Col B ! @Col @Code C ! @Col D }
{
@Rowa
    A { "@GraphCross" }
    B { @GraphCross }
    C { "@GraphPlus" }
    D { @GraphPlus }
@Rowa
    A { "@GraphSquare" }
    B { @GraphSquare }
    C { "@GraphFilledSquare" }
    D { @GraphFilledSquare }
@Rowa
    A { "@GraphDiamond" }
    B { @GraphDiamond }
    C { "@GraphFilledDiamond" }
    D { @GraphFilledDiamond }
@Rowa
    A { "@GraphCircle" }
    B { @GraphCircle }
    C { "@GraphFilledCircle" }
    D { @GraphFilledCircle }
@Rowa
    A { "@GraphTriangle" }
    B { @GraphTriangle }
    C { "@GraphFilledTriangle" }
    D { @GraphFilledTriangle }
@Rowa
@Rowa
    A { "@GraphNoLine" }
    B { @GraphNoLine }
@Rowa
    A { "@GraphSolid" }
    B { @GraphSolid }
@Rowa
    A { "@GraphDashed" }
    B { @GraphDashed }
@Rowa
    A { "@GraphDotted" }
    B { @GraphDotted }
@Rowa
    A { "@GraphDotDashed" }
    B { @GraphDotDashed }
@Rowa
    A { "@GraphDotDotDashed" }
    B { @GraphDotDotDashed }
@Rowa
    A { "@GraphDotDotDotDashed" }
    B { @GraphDotDotDotDashed }
}
These extra symbols may be used anywhere in your document except within
the right parameter of {@Code "@Graph"}; they are commonly used within
the caption options of {@Code "@Graph"}:
@ID @OneRow @Code @Verbatim {
@Graph
    rightcaption {
@GraphPlus @GraphSolid @GraphPlus  Boston
@GraphPlus @GraphDashed @GraphPlus  New York
@GraphPlus @GraphDotDashed @GraphPlus  Philadelphia
}
}
(You can also use them within the @Code objects option, which
is the way to place your key within the graph itself.)
Recall that unlike the other captions, @Code rightcaption is set using
the @Code "lines @Break" style rather than {@Code "clines @Break"}
(Section {@NumberOf captions}).  Adding this caption to the graph
from Section {@NumberOf data}, the complete result is
@CD @Graph
    rightcaption {
@GraphPlus @GraphSolid @GraphPlus  Boston
@GraphPlus @GraphDashed @GraphPlus  New York
@GraphPlus @GraphDotDashed @GraphPlus  Philadelphia
}
{
    @Data  points { plus }  pairs { solid }
    { 1720 12000  1730 13000  1740 15601  1760 15631  1770 15877 }

    @Data  points { plus }  pairs { dashed }
    { 1720 7000  1730 8622  1740 10451  1750 14255  1760 18000  1770 22667 }

    @Data  points { plus }  pairs { dotdashed }
    { 1720 10000  1730 11500  1740 12654  1750 18202  1760 23750  1770 34583 }

}
The first eight symbols have a @Code "symbolsize" option with the
usual meaning and the usual default value ({@Code "0.15f"}).  The
last four symbols have @Code "dashlength" and @Code "linewidth" options
with the usual default values, {@Code "0.2f"} and {@Code "0.5p"}
respectively, and a @Code "length" option, which determines the length
of the line drawn by each symbol; its default value is {@Code "1.0f"}.
@End @Section