Issue with a Manipulate expression for showing points sets and the alpha shape enclosing them

Question

I am using the alphaShapes2DC function from this post. It is a module which contains a Quiet operation. DelaunayMesh in a specified closed region - creating a concave hull from a set of points

I have a list containing 14 lists of 2d-points

prjs = {{{0, 1}, {1, 2}, {5, 1}}, {{2,2}}, ..., {{1, 5}, {6, 5}, {3, 5}}} 

with some sublists containing only one element and some duplicates so that the alphaShapes2DC function cannot run on such sublists.

I want to create a Manipulate function to display several sublists (with their polygon) at the same time.

Manipulate[
  If[Length @ prjs[[i]] > 2,
     Show[
       ListPlot[prjs[[i]], 
         Joined -> False, PlotStyle -> ColorData[97, "ColorList"][[i]]], 
       RegionPlot[Evaluate[alphaShapes2DC[DeleteDuplicates @ prjs[[i]], 6]],
         PlotStyle -> {ColorData[97, "ColorList"][[i]], [email protected]}, 
         BoundaryStyle -> {ColorData[97, "ColorList"][[i]], Thin}, 
         PlotRange -> All], PlotRange -> {{-15, 10}, {-10, 10}}],
       ListPlot[prjs[[i]], 
         Joined -> False,
         PlotStyle -> ColorData[97, "ColorList"][[i]],
         PlotRange -> {{-15, 10}, {-20, 20}}]],
  {{i, 1}, Range @ Length @ prjs}, 
    ContinuousAction -> True, ControlType -> TogglerBar]

Running this code first shows what I want.

But it turns bad when I click on a number in the bar — the polygon disappears.

Answer 1

Revision

First I contrive some test data since you did't provide any,

SeedRandom[3];
Block[{size},
  size := RandomInteger[{1, 20}];
  pts = RandomInteger[{1, 10}, {#, 2}] & /@ Table[size, 14]];

Now I generate lists for the items that will be plotted according to the buttons pressed on the toggler bar.

hullPlots = 
  Table[
    If[Length @ pts[[i]] > 2, 
      RegionPlot[ConvexHullMesh[pts[[i]]], 
        PlotStyle -> {ColorData[97][i], Opacity @ .2}, 
        BoundaryStyle -> {ColorData[97][i], Thin}], 
      Graphics[]], 
    {i, Length @ pts}];

ptPlots =
  Table[ListPlot[pts[[i]], PlotStyle -> ColorData[97][i]], {i, Length @ pts}];

Finally I write a Manpulate expression with a toggler bar control. The important thing to note about a toggler bar is that it returns a list of the buttons currently pressed.

DynamicModule[{hulls, pts},
  Manipulate[
    hulls = hullPlots[[selctn]];
    pts = ptPlots[[selctn]];
    Show[##, AxesOrigin -> {0, 0}, PlotRange -> {{0, 10}, {0, 10}}] & @@
      Join[hulls, pts],
    {{selctn, {1}, "i"}, Range @ Length @ ptPlots, TogglerBar}]]

The Manpulate expression comes up looking like this.

And here is what it might look like with several buttons pressed.

Note: If there are problems with alphaShapes2DC, I think that is an issue for a separate question, and I don't want to deal with it. That is why I used ConvexHullMesh instead.

BTW, if you would prefer all the points to always be displayed, that can be done with even simpler code. Like so.

DynamicModule[{hulls, pts},
  Manipulate[
    hulls = hullPlots[[selctn]];
    Show[##, AxesOrigin -> {0, 0}, PlotRange -> {{0, 10}, {0, 10}}] & @@
      Join[hulls, ptPlots],
    {{selctn, {1}, "i"}, Range @ Length @ ptPlots, TogglerBar}]]