GraphicsGrid and BarLegend combined

Question

I have constructed this contour plots for a project

ContourPlot[
  (2.1 - a^2 + 2.1 b) (-2 + (2.1 (1 + b))/a^2),
  {a, -1.5, -0.5}, {b, -1, 1},
  PlotRange -> All,
  ContourShading -> {RGBColor[0.16, 0.5, 0.5], RGBColor[0.51, 0.35, 0.25]},
  Contours -> {Automatic, 1},
  PlotLegends ->
   {BarLegend[Automatic, LegendMarkerSize -> 180, 
     LegendFunction -> "Frame", LegendMargins -> 5]},
  PlotLabel -> "Contour Plot", LabelStyle -> {Thick, Black},
  Mesh -> 1, MeshStyle -> Red, MeshFunctions -> {#1 &}
]

I have also the following contours

g2=(2.1 + (-1. - 6.6 a) a^2 + 2.1 (1 - 0.6 a^3) b) (-2. + (2.1 (1 + b))/   a^2 - 0.2 a (33 + 6.3 b))
g3=(2.1 + a^2 (-1. + 6.6 a) + 2.1 (1 + 0.6 a^3) b) (-2. + (2.1 (1 + b))/   a^2 + 0.2 a (33 + 6.3 b))
g4=(2.1 + a^2 (-1. + 14. a^2) + 2.1 (1 + 2. a^4) b) (-2. -    2. a^2 (-7 - 2.1 b) + (2.1 (1 + b))/a^2)

and I want to combine the four contours with GraphicsGrid and have a common BarLegend in the bottom of the figure (similar to the bar legend of the first contour plot). However I was unable to do that. Any suggestions?

Answer 1

This is kinda intro. You can improve this. You should define different range for each plot.

g = {(2.1 - a^2 + 
      2.1 b) (-2 + (2.1 (1 + b))/a^2), (2.1 + (-1. - 6.6 a) a^2 + 
      2.1 (1 - 0.6 a^3) b) (-2. + (2.1 (1 + b))/a^2 - 
      0.2 a (33 + 6.3 b)), (2.1 + a^2 (-1. + 6.6 a) + 
      2.1 (1 + 0.6 a^3) b) (-2. + (2.1 (1 + b))/a^2 + 
      0.2 a (33 + 6.3 b)), (2.1 + a^2 (-1. + 14. a^2) + 
      2.1 (1 + 2. a^4) b) (-2. - 
      2. a^2 (-7 - 2.1 b) + (2.1 (1 + b))/a^2)};

Legended[Multicolumn[
  Table[ContourPlot[g[[i]], {a, -1.5, -0.5}, {b, -1, 1}, 
    PlotRange -> All, 
    ContourShading -> {RGBColor[0.16, 0.5, 0.5], 
      RGBColor[0.51, 0.35, 0.25]}, Contours -> {Automatic, 1}, 
    PlotLabel -> "Contour Plot", LabelStyle -> {Thick, Black}, 
    Mesh -> 1, MeshStyle -> Red], {i, 4}], 2], 
 Placed[BarLegend[{{RGBColor[0.16, 0.5, 0.5], 
     RGBColor[0.51, 0.35, 0.25]}, {-1, 1}}, {-1, 0, 1}, 
   LegendLayout -> "Row", LegendMarkerSize -> 300, 
   LegendFunction -> "Frame", LegendMargins -> 5], Bottom]]