[Qgis-user] analysis of points and polygons

[john polo]

Users,
I have soil data from USDA NRCS, SSURGO. The soil data is for an area 
contained in a forest. I have loaded the soil polygons and have 
overlayed a point shapefile. The point shapefile comes from points 
randomly generated within the boundary of the forest. At each of the 
randomly generated points, I sampled soil and now I have a carbon value 
associated with each of the points. I would like to see now if there is 
a relationship between the carbon values I've gotten and the soil 
classifications. Is there a way to do with QGIS? What I'm looking for is 
close to the equivalent of an ANOVA, Carbon ~ Soil Class, and I don't 
know if there is something like that in GIS. My sampling was not 
stratified by soil class, so I realize it's going to be unbalanced, but 
I would like to attempt this nonetheless.

If there isn't an equivalent function for ANOVA, it seems that I need to 
figure out how to clip the soil classes, which are polygons, with the 
point data. I'm not sure, but I seem to remember not being able to clip 
shapefiles of different types. Is there a way to get the soil 
classification that would be associated with each point?

John Polo