[R] Return value associated with a factor

From: GL <pflugg_at_shands.ufl.edu>
Date: Mon, 21 Jun 2010 06:15:23 -0700 (PDT)

I am using the code below to extract census tract information. save.tract$state, save.tract$county and save.tract$tract are returned as factors. In the last three statements, I need to save the actual value of the factor, but, instead, the code is yielding the position of the factor. How do I instead return the value of the factor?

By way of example, for Lon=-82.49574 and Lat=29.71495, the code returns state = 1, county = 1 and tract = 161. The desired results are state=12, county = 001 tract = 002201.

#set libraries

library(UScensus2000tract)
library(gdata)
data(florida.tract)

#read input

dbs.in = read.delim("addresses_coded_new.txt", header = TRUE, sep = "\t",

                     quote="\"", dec=".")
                     

#instantiate output

more.columns <- data.frame( state=double(0),

                            county=double(0), 
                            tract=double(0)) 
                            
dbs.in <- cbind(dbs.in,more.columns)       

#fiure out how many times to loop

j <- nrow(dbs.in)

#loop through each lab/long and assign census tract

for (i in 1:j) {         

index<-overlay(SpatialPoints(cbind(dbs.in$Lon[i],dbs.in$Lat[i])),florida.tract)

         save.tract<-florida.tract[index,] 
         dbs.in$state[i] <- save.tract$state #this is returning the position
in the list instead of the value
         dbs.in$county[i] <- save.tract$county #this is returning the
position in the list instead of the value
         dbs.in$tract[i] <- save.tract$tract #this is returning the position
in the list instead of the value

    }         

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Received on Mon 21 Jun 2010 - 13:19:25 GMT

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