How to order legend in Show?

Question

I've asked this question in Wolfram community and have not received a response.

I am wondering why when I use Show to combine 6 plots, the plot legend does not show in order? The order should be 150, 250, 350, 450, 550, 650. However when I step through Show adding one plot at a time, I notice that Mathematica does something weird with the order of the legend, and in the end the order is 650, 150, 250, 350, 450, 550. How can I get the order of the Legend or Show to be correct, such that there is a logical sequence of the label? I have attached some code below to show what's happening:

 data = {
     {0., 23.1628, 15., 12., 5., 2., .75, 0.0},
     {0., 53.611, 100., 83.27448, 40., 33., 25., 10.0},
     {0., 71.7055, 100., 79, 72.996, 30.76314, 17., 15.},
     {0., 71.92428, 100., 100, 83.35182, 41.09816, 35., 10.0},
     {0., 75.87498, 100., 100., 88.65755, 87.0691, 34.27131, 20.},
     {0., 100., 100., 100., 88.65755, 87.0691, 80.4311, 39.40}
     } // TableForm;

time = {0., 120., 300., 600., 900., 1200., 1500., 1800.};

activity = Table[Transpose[{time, data[[1, i]]}], {i, 1, 6}];

tickSpecs = {{{0, "0"}, {120, "2"}, {300, "5"}, {600, "10"}, {900,
     "15"}, {1200, "20"}, {1500, "25"}, {1800, "30"}}, Automatic};

label = {"150 ", "250 ", "350 ", "450 ", "550 ", "650 "};
colors = {Black, Red, Orange, Green, Blue, Purple, Magenta};


Plots = Table[
     ListPlot[activity[[i]],

    PlotRange -> All,

    PlotStyle -> {Darker[colors[[i]]], Dashing[{0.05}], Thick,
      AbsolutePointSize[12]},
    Joined -> True,
    Mesh -> All,
    Ticks -> {Automatic, None},
    FrameTicks -> tickSpecs,
    Frame -> {Left, Bottom},
    FrameStyle -> Thick,
    Axes -> False,
    LabelStyle -> {FontSize -> 20, FormatType -> Bold},
    ImageSize -> 450,
    PlotLegends ->
     LineLegend[{label[[i]]},
      LabelStyle -> Directive[Bold, 15],
      LegendMarkerSize -> Automatic]],
{i, 1, 6}];

Show[Plots]

Answer 1

Also, without the fuss of tables and Showand disregarding unnecessary options:

ListLinePlot[activity,
 FrameTicks -> tickSpecs, 
 Frame -> {Left, Bottom}, FrameStyle -> Thick, Axes -> False, 
 LabelStyle -> {FontSize -> 20, FormatType -> Bold}, 
 PlotStyle -> (Directive[Darker@#, Dashing[{0.05}], Thick] & /@ colors), 
 PlotLegends -> LineLegend[label, LabelStyle -> Directive[Bold, 15]], 
 PlotMarkers -> ({Graphics[{Darker@#, Disk[]}], .05} & /@ colors)]

Answer 2

I've run into several issues like this with the legends and quite frankly, trying to investigate the cause/fix it is probably more trouble than worth. Instead, here's a work around:

(* Your code without the legends *)
Plots = Table[
   ListPlot[activity[[i]], PlotRange -> All, 
    PlotStyle -> {Darker[colors[[i]]], Dashing[{0.05}], Thick, 
      AbsolutePointSize[12]}, Joined -> True, Mesh -> All, 
    Ticks -> {Automatic, None}, FrameTicks -> tickSpecs, 
    Frame -> {Left, Bottom}, FrameStyle -> Thick, Axes -> False, 
    LabelStyle -> {FontSize -> 20, FormatType -> Bold}, 
    ImageSize -> 450], {i, 1, 6}];

(* Construct legends separately *)
Row[{
    Show[Plots],
    LineLegend[Directive@{Darker@#, Thick, Dashing[{0.05}]} & /@ Most@colors, label, 
        LabelStyle -> Directive[Bold, 15], LegendMarkerSize -> Automatic]
}]

I think this might be a bug, since this errant behaviour does not occur in Mathematica 10 on the Raspberry Pi.

Answer 3

There may be cases where Show[] is preferred (e.g. when combining ListPlot and Plot). In that case nesting the Show function was found to preserve the order of the legend items.

In the above example, the following was found to preserve the legend order.

Show[Plots[[1]]];
Show[%, Plots[[2]]];
Show[%, Plots[[3]]];
Show[%, Plots[[4]]];
Show[%, Plots[[5]]];
Show[%, Plots[[6]]]

One may use the following function.

Show2[plots__] := Fold[Show,  Show[(List @ plots)[[1]]],  (List @ plots)[[2 ;; -1]]]

But since Plots is a list, the head 'List' should be removed with the @@ operator to obtain a sequence:

 Show2 @@ Plots

Answer 4

You can do a simple manual fix like so :-

Show[Extract[Plots, {{5}, {4}, {3}, {2}, {1}, {6}}]]

Answer 5

ListLinePlot[Legended[#, Style[#2, Bold, 15]] & @@@ Transpose[{activity, label}],
 Axes -> False, FrameTicks -> tickSpecs, Frame -> {True, True, False, False},  
 FrameStyle -> Directive[FontSize -> 20, FontWeight -> Bold],
 PlotStyle -> (Thread[{Darker /@ colors, Dashing[{0.05}], Thick}]),
 PlotMarkers -> ({Graphics[{Dynamic@CurrentValue["Color"], Disk[]}], .05})]