how to calculate Moran's I based on the distance along river

[ddlang]

I have some monitoring sites in a basin. I wan to calculate the Moran's I based on the distance along the river instead of Euclidean distance. How to do that? Thanks!

[whuber]

Calculate the distances (perhaps with a set of costdistance calculations based on a raster representation of the river or with a network-based calculation based on a vector representation). Then proceed as usual. Detailed guidance for computing Moran's I from a set of (arbitrary) distances appears, inter alia, at http://www.ats.ucla.edu/stat/r/faq/morans_i.htm.

[ddlang]

thanks. how to calculate the distance along river network? Is there any tool in ArcGIS?

[whuber]

To calculate distances along a river network, either use Network Analyst (treating the rivers as a route) or Spatial Analyst (with its CostDistance functionality).