plotting legends in Mathematica

Question

How do you plot legends for functions without using the PlotLegends package?

Answer 1

I, too, was disappointed by the difficulty of getting PlotLegend to work correctly. I wrote my own brief function to make my own custom figure legends:

makePlotLegend[names_, markers_, origin_, markerSize_, fontSize_, font_] :=    Join @@ Table[{     Text[       Style[names[[i]], FontSize -> fontSize, font],        Offset[         {1.5*markerSize, -(i - 0.5) * Max[markerSize,fontSize] * 1.25},         Scaled[origin]       ],       {-1, 0}     ],     Inset[       Show[markers[[i]], ImageSize -> markerSize],       Offset[         {0.5*markerSize, -(i - 0.5) * Max[markerSize,fontSize] * 1.25},         Scaled[origin]       ],       {0, 0},        Background -> Directive[Opacity[0], White]     ]   },   {i, 1, Length[names]} ]; 

It is flexible, but not so easy to use. "names" is a list of strings to render in the legend; "markers" is a list with the same length as "names" of Graphics objects representing the plot markers or graphics to render; "origin" is a two-element list with the absolute horizontal and vertical position of the upper-left corner of the legend; "markerSize" is the number of points to scale the markers to; "fontSize" is the font size; "font" is the name of the font to use. Here is an example:

Plot[{x, x^2}, {x, 0, 2}, PlotStyle -> {Blue, Red},   Epilog -> makePlotLegend[     {x, x^2},     (Graphics[{#, Line[{{-1, 0}, {1, 0}}]}]) & /@ {Blue, Red},     {0.9, 0.3},     12,     12,     "Arial"   ] ] 

Answer 2

I would also be very interested in an answer to this question.

To tell you what is wrong with PlotLegends: It is terribly unstable and in many instances doesn't work at all.

Here is an example where PlotLegends screws up completely. Output is from Mathematica 7.0:

Assume that we have measured some data points corresponding to a number of functions, and we want to show how well they compare to the ideal function, or maybe how well they match with a calculated fit. No problem! We'll just Show[] the smooth plot together with a ListPlot of the data points, right?

It could look something like this:

Show[  Plot[{Sin[x], Sinh[x]}, {x, -Pi, Pi}],  ListPlot[Join[{#, Sin[#]} & /@ Range[-Pi, Pi, .5],                 {#, Sinh[#]} & /@ Range[-Pi, Pi, .5]]]  ] 

Now we'd like to put a legend on the plot, so readers will know what on earth they're looking at. Easier said than done, mister! Let's add the PlotLegend to the Plot[]:

Show[   Plot[{Sin[x], Sinh[x]}, {x, -Pi, Pi}, PlotLegend -> {Sin[x], Sinh[x]}],   ListPlot[Join[{#, Sin[#]} & /@ Range[-Pi, Pi, .5],                  {#, Sinh[#]} & /@ Range[-Pi, Pi, .5]]]  ] 

This looks GREAT! Publish immediately!

For such a basic and ubiquitously needed functionality, it sure has been a lot of work to find an alternative to PlotLegend that just works. The best alternative I've found so far has been to meticulously construct a list of plotstyles, then construct the legend by hand, and finally to show it together with the plot using ShowLegend[]. (See for example here) It's possible, but a lot of work.

So if anyone knows of a workaround to make PlotLegend work, an alternative package that works better, or just a neat way to get legends that can be automated easily, I would be very grateful! It would certainly make life a little bit easier.