topic Re: Density points to equally divided polygons in Geoprocessing Questions

Density points to equally divided polygons

RobertoDeDeus — Thu, 14 Jan 2016 18:14:42 GMT

How do I convert a point layer into multiple polygons? Ideally each polygon would take into account the weight of each point.

EDIT: Just to clarify my intention. I have a layer with 2,000 points. I want to end up with a polygon layer which has three polygons where each polygon covers the area of 1/3 of those points.

Message was edited by: Roberto DeDeus

Re: Density points to equally divided polygons

WesMiller — Thu, 14 Jan 2016 18:21:15 GMT

You could Using graduated symbols—Help | ArcGIS for Desktop

or you could buffer each point based on the field Buffer—Help | ArcGIS for Desktop

And for density you'll want

Point Density—Help | ArcGIS for Desktop

Kernel Density—Help | ArcGIS for Desktop

EDIT:

i missed Using proportional symbols—Help | ArcGIS for Desktop

Re: Density points to equally divided polygons

DanPatterson_Retired — Thu, 14 Jan 2016 18:53:33 GMT

a voronoi diagram will subdivide space from input points.

Examining local variation—Help | ArcGIS for Desktop in geostatistical analyst

Create Thiessen Polygons—Help | ArcGIS for Desktop with an advanced license

or Triangulation tools... http://www.arcgis.com/home/item.html?id=6e9bc6cbf93d4939b2eb04ff8519be47

my humble but free offering

Re: Density points to equally divided polygons

DanPatterson_Retired — Fri, 15 Jan 2016 01:44:50 GMT

Well your modified question, is indeed different... perhaps Aggregate Points—Help | ArcGIS for Desktop

might be a first step, although getting to the target of 3 polygons and 3 only may be a bit out of its realm. But you will need an Advanced license. And perhaps Aggregate Polygons—Help | ArcGIS for Desktop could be used in association with it after the initial clustering

Re: Density points to equally divided polygons

DarrenWiens2 — Fri, 15 Jan 2016 04:57:44 GMT

Can you provide a picture of what you hope to accomplish? There are (almost) an infinite number of solutions to this problem the way I see it.

Re: Density points to equally divided polygons

XanderBakker — Fri, 15 Jan 2016 12:30:13 GMT

A rather manual way (and using an Advanced license) could be:

Create Thiessen Polygons based on the input points
Generate a Near table from the points to the polygons limiting the maximum number of closest matched to a third of the total number of points and not limiting the search distance (this will create a huge table in your case using 2000 points)
From the table, create two relates. One towards the points using the IN_FID matching the OBJECTID and one towards the thiessen polygons using the NEAR_FID matching the OBJECTID of the polygons.
In the point featureclass, select a single extreme point:

Open the attribute table of the points and use the Relate to select the nearest polygons:

In the Near table use the relate to the polygons to select the corresponding Thiessen polygons:

Add a new numeric field to the polygons and fill the field with the value 1 (group 1)
Do the same based on an extreme point located at the opposite of the area (assign value 3)

Select the features where the new goup field IS NULL
Fill that selection with value 2:

You can make the result a bit more presentable by clipping it with the area of interest or using the Minimum Bounding Geometry tool to create a ConvexHull, buffer that with a representative distance and clip it. Dissolve the polygons by the group field:

This is very manual and you may have a problem when using 2000 points. In my case using 300 point the number of records in the Near table was 300 * 100 = 30000. In you case it will be 2000 * 667 = 1334000.

I'm sure there must a nice algoritm implemented in Python to do the job...

Re: Density points to equally divided polygons

XanderBakker — Fri, 15 Jan 2016 12:31:24 GMT

Dan, that's a great Thiessen tool you uploaded to ArcGIS Online! Thanx for sharing!

Re: Density points to equally divided polygons

XanderBakker — Fri, 15 Jan 2016 12:33:33 GMT

BTW, it would be nice if the Grouping Analysis—Help | ArcGIS for Desktop would do the job, but it has no option to divide into equal groups.

Maybe the Location-allocation analysis—Help | ArcGIS for Desktop could be helpful?