Why is plotGrid acting this way?

Question

A couple of days ago I discovered the plotGrid function from this answer here (written by @Jens). Since it seemed interesting I tried playing around with it a bit and I'm currently facing a problem which I don't really understand...

Consider the following code:

(* taken from: https://mathematica.stackexchange.com/a/6882/53872 *)
Options[plotGrid] = {ImagePadding -> 40};
plotGrid[l_List, w_, h_, opts : OptionsPattern[]] := 
 Module[{nx, ny, sidePadding = OptionValue[plotGrid, ImagePadding], 
   topPadding = 0, widths, heights, dimensions, positions, 
   frameOptions = 
    FilterRules[{opts}, 
     FilterRules[Options[Graphics], 
      Except[{ImagePadding, Frame, FrameTicks}]]]}, {ny, nx} = 
   Dimensions[l];
  widths = (w - 2 sidePadding)/nx Table[1, {nx}];
  widths[[1]] = widths[[1]] + sidePadding;
  widths[[-1]] = widths[[-1]] + sidePadding;
  heights = (h - 2 sidePadding)/ny Table[1, {ny}];
  heights[[1]] = heights[[1]] + sidePadding;
  heights[[-1]] = heights[[-1]] + sidePadding;
  positions = 
   Transpose@
    Partition[
     Tuples[Prepend[Accumulate[Most[#]], 0] & /@ {widths, heights}], 
     ny];
  Graphics[
   Table[Inset[
     Show[l[[ny - j + 1, i]], 
      ImagePadding -> {{If[i == 1, sidePadding, 0], 
         If[i == nx, sidePadding, 0]}, {If[j == 1, sidePadding, 0], 
         If[j == ny, sidePadding, topPadding]}}, AspectRatio -> Full],
      positions[[j, i]], {Left, Bottom}, {widths[[i]], 
      heights[[j]]}], {i, 1, nx}, {j, 1, ny}], 
   PlotRange -> {{0, w}, {0, h}}, ImageSize -> {w, h}, 
   Evaluate@Apply[Sequence, frameOptions]]]


GenerateRandomMeshRegion[] := Module[{},
   pts = RandomReal[{2, 1}, {25, 2}];
   test = VoronoiMesh[pts];
   Return[Show[test]]];

TableOfPlots = 
  Table[GenerateRandomMeshRegion[], {n, 1, 2}, {m, 1, 2}];

plotGrid[TableOfPlots, 400, 400, ImagePadding -> 0]

with output:

Can someone explain to me why there is a horizontal gap between the different MeshRegions and how you would fix that? If I try the example @Jens gives in his answer there is no such vertical gap, so I'm wondering where I added it by accident...

m_goldberg · Accepted Answer · 2019-05-16T11:48:54.033

There is a gap between the columns of the mesh diagrams because VoronoiMesh, by default, adds a little plot range padding to its graphics. The gap can be eliminated by giving VoronoiMesh the option PlotRangePadding -> 0. Like so:

generateRandomMeshRegion[] :=  
  VoronoiMesh[RandomReal[{1, 2}, {25, 2}], PlotRangePadding -> 0]
SeedRandom[42]; plots = Partition[Table[generateRandomMeshRegion[], 4], 2];
plotGrid[plots, 400, 400, ImagePadding -> 0]

Why is plotGrid acting this way?

1 Answers1