Sunday, April 28, 2013

How to calculate covariates as aggregates of neighborhood buffer of points in ArcGIS 10.0

If we have point levels data, we often want to calculate the value of certain covariates that can depict it's influence within neighborhood(or distance buffer) as environmental risk factors on an outcomes. These covariates are simply the aggregates a covariates value of each points, whithin neighborhood/a circle of buffer for example.

Then the steps are:
1. Make sure we have shape file point feature with relevant attributes (covariates) table within.
2. Create buffer (In Geoprocessing Toolbox) of whatever radius we want from the point feature.
3. Perform "Spatial Joint" from Analysis toolbox - Overlay-Spatial Joint.
4. Choose the new buffer polygon feature you just created as target feature.
5. Choose our point feature as joint feature.
6. Name the output shape file and set the directory we would like to save it.
7. Choose one to one relationship.
8. Looking the variables we would like to aggregate but with sign like "...._1" (because the buffer polygon also contain the same variable that taken from the original point feature, so ArcGIS try to make it different by adding 1).
9. Right click on it and look for merge rule "sum" ( I assume that we need a sum within the buffer)
10. Set the match option as "Contain.
11. Click OK

Tips: When you work with big data, you better try it first with small number of point features and check the result out whether that's what you really want.