Show areas defined by sets of latitude/longitude

Question

I have a list of casinos. Each casino has:

• latitude
• longitude
• boss (a single boss runs from 1 to 50 casinos)

Sample:

40.642 -73.997 Freddy Queens
40.680 -73.985 Freddy Queens
40.697 -73.949 Freddy Queens
40.651 -73.968 Freddy Queens
40.772 -73.981 Manhattan Michael
40.813 -73.939 Manhattan Michael
40.755 -74.000 Manhattan Michael
40.781 -73.964 Manhattan Michael
40.721 -74.062 Nicole Je. Polizzi
40.750 -74.042 Nicole Je. Polizzi
40.694 -74.090 Nicole Je. Polizzi
[... 70,000 casinos for 27,000 bosses ...]

From this data I want to generate a map like this:

(hand-drawn representation, not accurate)

One color per boss. The casinos of each boss should not "overlap" too much. The final goal is to find anomalies (casinos that should be transferred to a different boss because they are clearly in that boss' "territory"). Boss "territories" do not match any official geographical subdivisions, for all that matters the same problem could be set on Mars (Earth map background would be nice though).

Is there a webapp (desktop program also OK) to which I could feed this data (CSV) and that would show this kind of map? It can look different, for instance monochrome areas would be OK too, as long as it can be used to detect anomalies.

Answer 1

1. For each boss you need to calculate the convex hull of their locations as this defines their "territory".

2. Casinos that exist in more than one of these regions (use RegionMember) are potential targets for reallocation. Your dataset does not have any conflicts so I leave this to you.

   2.1 You can highlight these by using a different marker and style. Add a click event that will pop up the territories that overlap and assign it to the one you like.

   2.2 If the criteria is formulaic then you can just code it through.

3. Replot.

I only do part one as there are no conflicts. However, I think I should leave some of the fun of 2 to you. If you attempt 2 in Mathematica and need some help then pop over the the Mathematica SE for assistance.

Mathematica Code

I just imported from the string directly for this one instead of making a text file.

dat = ImportString[ "40.642,-73.997,Freddy Queens
  40.680,-73.985,Freddy Queens
  40.697,-73.949,Freddy Queens
  40.651,-73.968,Freddy Queens
  40.772,-73.981,Manhattan Michael
  40.813,-73.939,Manhattan Michael
  40.755,-74.000,Manhattan Michael
  40.781,-73.964,Manhattan Michael
  40.721,-74.062,Nicole Je.Polizzi
  40.750,-74.042,Nicole Je.Polizzi
  40.694,-74.090,Nicole Je.Polizzi",
  "CSV"];

I use an Association here but you may want to use Dataset for your larger set. I also swap the order of the co-ordinates as they are not in the conventional order (they were plotting in Antarctica).

(* Calculate the territory and get a colour for each boss *)
bossPts = Association @@ KeyValueMap[
   Function[{key, value},
    With[{pts = value[[All, {2, 1}]]},
     key -> <|
       "Casinos" -> pts,
       "Territory" -> Identity @@@ MeshPrimitives[ConvexHullMesh[pts], 0],
       "Colour" -> ColorData["DarkRainbow"][RandomReal[]]
      |>
     ]
    ], GroupBy[dat, Last]];

I tooltip the territory with the boss' name and plot everything in the boss' colour.

KeyValueMap[
  Function[{key, value},
   {
    value["Colour"],
    {GeoStyling[Opacity[.7]], 
     Tooltip[Polygon[value["Territory"]], key]},
    {PointSize[0.02], Point /@ value["Casinos"]}
    }
   ],
  bossPts] // GeoGraphics

Hope this helps.

Answer 2

Use Google's MyMaps to map the lats and longs. Use a different color for each cluster/territory/"boss". Adjust the cluster/territory/boss as necessary after mapping each cluster. Draw lines and connect the dots.

If you really want to create polygons automatically, check out QGIS, the open-source GIS package, and PostGIS.