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34 lines
1.2 KiB
34 lines
1.2 KiB
## Functions to create data for DC Area
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## (DC & surrounding jurisdictions, including independent cities)
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select.dcarea <- function(dta) {
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## Arguments: `dta`: dataset from from which to select observations in
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## the DC Area
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## Returns: dataset containing only observations from the DC area
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## Identify counties to keep in DC Area dataset using FIPS county codes
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counties <- c(
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'110001' # D.C.
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, '240031' # Montgomery County
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, '240033' # Prince George's County
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, '510013' # Arlington County
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, '510059' # Fairfax County
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, '510510' # Alexandria city
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, '510600' # Fairfax city
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, '510610' # Falls Church city
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)
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## Select counties using regular expression based on FIPS codes above
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## and common `GISJOIN` variable
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re <- paste0('^G', counties, collapse = '|')
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dcarea <- dta[grep(re, dta$GISJOIN, perl=TRUE),]
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## Replace factor variables to contain only levels in the DC area
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if('COUNTY' %in% names(dcarea)) {
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dcarea$COUNTY <- factor(dcarea$COUNTY)
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}
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if('STATE' %in% names(dcarea)) {
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dcarea$STATE <- factor(dcarea$STATE)
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}
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return(dcarea)
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}
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