# Build measure of state change

I want to be able to build a measure in ArcGIS (ArcMap).

(1) I have some shapefiles of sovereign states by centuries. These are polygons with the name of the state as ID. (2) Moreover, I have a shapefile of current European regions at NUTS 2 level.

I would like to get a measure of the average number of States that existed in a given NUTS 2 region, over centuries. I have tried to build such a measure for days now.

My bet was to build this measure by using the tool Union. Take two maps of sovereign states for 1000 and 1100, for example, unionize them. Union will give me a new attribute table with the polygons non-intersecting at t=1000, t=1100 and those intersecting in between.

What I want is a measure that will tell me how many States did rule in a given polygon. Project the two sovereign states shapefiles for 1000 and 1100. Some polygons will likely maintain their borders, hence the measure should give 1 for the latter. In other cases, the polygon in the first period will be crossed by another polygon. This will give three polygons: two that belong to the same states as before and another one (the intersection) which was belonging to state A in period t= 1000 and now to B in period t=1100. The measure should give 2 for this polygon. Then I was thinking about using something like Spatial Join to be able to get the average count of polygons in a NUTS 2 region.

However the very first problem is that the attribute table that I get with GIS after using the Union tool as polygons with the State related at t=1000 and t= 11000 but I don't ever know how I can convert these different names to count (and a number).

• Intersect with 1000, use summary statistics, where case field is NUTS' id. Use attribute join by that id to transfer frequency to nuts table, perhaps to a new field. Apr 7, 2019 at 3:38
• Are you looking for a count such as Ghana: 13, Croatia: 1, Mumha: 54, etc...?
– Aaron
Apr 7, 2019 at 4:02
• Hello, actually at the end of the day I am looking for a count, say 5 in Lombardia, 10 in Piemonte, etc. Apr 7, 2019 at 5:12