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Sometimes, it is useful to plot only a single legend for several figures, for example, those were produced by DensityPlot. The following is an example from the document.

Generate a numerical solution to plot:

usol = NDSolveValue[{D[u[t, x], t] == D[u[t, x], x, x], u[0, x] == 0, u[t, 0] == Sin[t], u[t, 5] == 0}, u, {t, 0, 10}, {x, 0, 5}]

The first plot for $t\in[0,2]$ and the 2nd one for $t\in[2,10]$

dplt1 = DensityPlot[usol[t, x], {t, 0, 2}, {x, 0, 5}, PlotLegends -> Automatic, PlotRange -> All, ImageSize -> 200] dplt2 = DensityPlot[usol[t, x], {t, 2, 10}, {x, 0, 5}, PlotLegends -> Automatic, PlotRange -> All, ImageSize -> 200]

They give two plots with different legend ranges.

enter image description here enter image description here

My questions are two-fold:

  1. How to generate a single legend with the same max and min values for both figures. The max and min could be observed by firstly using PlotLegends -> Automatic and then plot a uniform legend with the global max/min values;

  2. What is an appropriate method to export such a legend in .eps, to be edited further in graphic software, e.g. Illustrator? I have tried to export the automatically produced bar-legend with Export[".eps"], however, I found its ticks are not short lines but like rectangles, which are hard to edit, e.g. thickness or color.

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  • $\begingroup$ Why not just use {t, 0, 10}, {x, 0, 5} to make a single densityplot? $\endgroup$ Commented Aug 25, 2022 at 2:40

2 Answers 2

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Legend can be generated separately with ArrayPlot using common color function. For better labels you can use MaTeX.

(* set default color for out of range data *) BACKGROUND = LightBlue ; (* set color scheme *) SCHEME = "SunsetColors" ; (* set data interval *) {MIN, MAX} = {-1.0, +1.0} ; (* set color function *) COLOR = With[ {BACKGROUND=BACKGROUND, SCHEME = ColorData[SCHEME], MIN = MIN, MAX = MAX}, If[MIN <= # <= MAX, SCHEME[Rescale[#, {MIN, MAX}]], BACKGROUND] & ] ; (* set plot size *) {HSIZE, VSIZE, LSIZE} = {300, 300, 20} ; (* set padding *) PADDIND = 30 ; (* generate legend *) SIZE = 1000 ; DATA = Reverse[Transpose[{Subdivide[MIN, MAX, SIZE]}]] ; LEGEND = ArrayPlot[ DATA, PlotLegends -> False, Frame -> False, ImagePadding -> None, PlotRangePadding -> None, ColorFunction -> COLOR, ColorFunctionScaling -> False, DataRange -> {{0, 1}, {MIN, MAX}} ] ; LEGEND = Show[ Graphics[ {White, Opacity[0], Apply[Rectangle, Transpose[N[{{0.0, 1.0}, {MIN, MAX}}]]]}, AspectRatio -> HSIZE/LSIZE, Frame -> True, FrameTicks -> {{None, All}, {None, None}}, FrameStyle -> Directive[{Black}], FrameTicksStyle -> Directive[{Black, 12}], PlotRangePadding -> None, ImagePadding -> {{0, PADDIND},{PADDIND,PADDIND}}, ImageSize -> {Automatic, VSIZE} ], LEGEND ] ; (* generate plots *) ClearAll[foo] ; foo[x_, y_] := +Cos[2*x*y]^2 ; ClearAll[bar] ; bar[x_, y_] := -Sin[2*x*y]^2 ; plt1 = DensityPlot[foo[x, y], {x, -1, 1}, {y, -1, 1}, PlotLegends -> False, ColorFunction -> COLOR, ColorFunctionScaling -> False, ImagePadding -> PADDIND, PlotRangePadding -> None, ImageSize -> {VSIZE, HSIZE}, FrameTicks -> {{All, None}, {All, None}}, FrameStyle -> Directive[{Black}], FrameTicksStyle -> Directive[{Black, 12}]] ; plt2 = DensityPlot[bar[x, y], {x, -1, 1}, {y, -1, 1}, PlotLegends -> False, ColorFunction -> COLOR, ColorFunctionScaling -> False, ImagePadding -> PADDIND, PlotRangePadding -> None, ImageSize -> {VSIZE, HSIZE}, FrameTicks -> {{All, None}, {All, None}}, FrameStyle -> Directive[{Black}], FrameTicksStyle -> Directive[{Black, 12}]] ; (* combine plots *) result = Grid[ { { Labeled[plt1, {Style["x", Bold, 12], Style["y", Bold, 12]}, {Bottom, Left}, RotateLabel -> True, Spacings -> 0.1], Labeled[plt2, {Style["x", Bold, 12], Style["y", Bold, 12]}, {Bottom, Left}, RotateLabel -> True, Spacings -> 0.1], Labeled[LEGEND, Style["color", Bold, 12], Left, RotateLabel -> True, Spacings -> 0.1] } }, Alignment -> Center, Spacings -> 0 ]

enter image description here

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colorBar[arg_] := ColorData["GreenPinkTones"][Rescale[arg, {-2, 2}]] plots = DensityPlot[#, {x, 0, 2 \[Pi]}, {y, 0, 2 \[Pi]}, ColorFunction -> (colorBar[#] &), ColorFunctionScaling -> False, ImagePadding -> 80, ImageSize -> 350, LabelStyle -> {FontFamily -> "LM Roman 12", Black, FontSize -> 16}, FrameLabel -> {"x", "y"}, PlotPoints -> 60] & /@ {Sin[x y], 2 Sin[x y]}; compinplots = Grid[{# & /@ plots}, Spacings -> {-10, -10}]; barlgns = BarLegend[{ColorData["GreenPinkTones"], {-2, 2}}, LegendLayout -> "Column", Charting`TickSide -> Right, LabelStyle -> {FontFamily -> "LM Roman 12", Black, FontSize -> 16}, LegendMarkerSize -> 120, ColorFunctionScaling -> True, LegendLabel -> "Z"]; final = Legended[compinplots, Placed[barlgns, {0.95, 0.5}]]

enter image description here

if you have more plots you can also this

Legended[Grid[{# & /@ plots, # & /@ plots}, Spacings -> {-10, -11.3}], Placed[barlgns, {0.95, 0.5}]]

enter image description here

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