Aggregate points into polygon?

[ts]

Hi - I’m curious if I have a number of points (ie: lats and longs) in a json file if D3 can aggregate those into a polygon for me.  e.g:  three data points in NYC would be aggregated into a polygon for New York State - so i could show a choropleth map comparing the number of cases of the flu in NY state (here, three cases) vs. the number of cases in other states.  

If so, is there a tutorial out there on how to do this?  I've looked around but haven't found one.  

If not, am thinking I would do the aggregation in PostGIS.  My SQL is not very good though, so if anyone has any suggestions on tutorials for doing that as well that'd be welcome. 

Thanks.  

[Tito]

Can we give us sample data points? Maybe we can start from there. Do you want to see the whole US map overlaid with your flu stats?

Can you draw up a sample image manually of what you want to see?