How Do I Add Legends to Charts and Plots?

With Mathematica, you can easily create plots of two-dimensional data or represent data in graphics such as bar charts or pie charts. Very often it will be useful to create legends for these graphics to aid in the interpretation of your data. The standard add-on package Graphics`Legend` offers a set of flexible graphics objects to do just that.

Legends for Plots of Functions

When using the function Plot, the option PlotLegend may be used to quickly and automatically add a legend.

Example 1.1

Plot[{Sin[x], Cos[x]}, {x, -2 Pi, 2 Pi},
    PlotStyle -> {RGBColor[0, 1, 0], RGBColor[0, 0, 1]},
    PlotLegend -> {"Sine", "Cosine"}]

By default, Mathematica will automatically choose a size and location for the legend box. You may use LegendPosition and LegendSize to specify where you want your legend to go and how big it should be. These specifications should be made using the coordinate system below. Note that the coordinate system for LegendPosition and LegendSize is independent of your coordinate system for your plot.

Below is an example of manually defining the size (0.5 wide by 0.25 high) and position (0.5, 0.3) for the legend.

Example 1.2

Plot[{Sin[x], Cos[x]}, {x, -2 Pi, 2 Pi},
    PlotStyle -> {RGBColor[0, 1, 0], RGBColor[0, 0, 1]},
    PlotLegend -> {"Sine", "Cosine"},
    LegendPosition -> {.5, .3},
    LegendSize -> {.5, .25}]

Legends for Plots of Data

Legends can also be added to data plots using the function ListPlot in essentially the same way as function plots.

Example 2.1

MultipleListPlot[{datalist1, datalist2},
    PlotJoined -> {True, False},
    PlotStyle -> {RGBColor[1, 0, 0], RGBColor[0, 0, 1]},
    PlotLegend -> {"Sine", "Cosine"}]

Legends for Charts and Other Graphics

The option PlotLegend cannot be used to add legends to other objects such as BarChart, PieChart, etc. For these objects, the legend must be created using the function ShowLegend[graphics object, legend object] and Mathematica's library of graphics primitives.

Start with a simple bar chart as follows.

And now add a legend by wrapping the previous chart in the function ShowLegend and defining the legend's fields and labels.

Example 3.1

Of course the same technique can be used on any graphic or array of graphics.

Example 3.2

ShowLegend[
DisplayTogetherArray[
  {{PieChart[{11, 18, 12}, PieLabels -> None, PlotLabel -> "Q1 `98"],
    PieChart[{13, 21, 12}, PieLabels -> None, PlotLabel -> "Q2 `98"],
    PieChart[{14, 20, 13}, PieLabels -> None, PlotLabel -> "Q3 `98"]},
   {PieChart[{14, 26, 10}, PieLabels -> None, PlotLabel -> "Q4 `98"],
    PieChart[{18, 23, 16}, PieLabels -> None, PlotLabel -> "Q1 `99"],
    PieChart[{17, 25, 16}, PieLabels -> None, PieExploded -> All, PlotLabel -> "Q2 `99"]}}],
   {{{RGBColor[1, 0, 0], "Helen"},
     {RGBColor[0, 1, 0], "Joe"},
     {RGBColor[0, 0, 1], "Bob"}},
   LegendPosition -> {-0.5, .75},
   LegendSize -> {1, .4},
   LegendLabel -> "Acme Company Sales",
   LegendOrientation -> Horizontal,
   LegendShadow -> None}
]