Errata

Use of Sys.sleep(0.5) #this pause helps keep Yahoo happy
still throws a lot of "xml parsing or http error: 1: failed to load HTTP resource" errors. I've tried 1.0 and get fewer errors and 1.5 which so far has produce one error.

Note from the Author or Editor:
This is a good tip for others who are seeing a lot of timeouts.

I've been trying to get the Yahoo Maps API sample to work, I've signed up for my own developer's key. When I do it through the XML example I get:
failed to load HTTP resource
Error: 1: failed to load HTTP resource

When I do it through the restful API, I get the following with my own appID or using the one in the book:

<?xml version="1.0" encoding="UTF-8"?>
-<Error xmlns="urn:yahoo:api">
<!-- ydn3.ls.ac4.yahoo.com uncompressed/chunked Fri Aug 24 19:58:34 UTC 2012 -->
The following errors were detected: <Message>backend fetch error 404</Message> </Error>

Please help.

Note from the Author or Editor:
Thank you for bringing this to my attention. It appears Yahoo has discontinued this version of their geocoding API, but the replacing the geocodeAddresses function with the one below will work with their newer PlaceFinder API.

#input:vector of streets
#output:data frame containing lat/longs in PBSmapping-acceptable format
#this revised function uses the newer Yahoo PlaceFinder API
geocodeAddresses<-function(myStreets){
myGeoTable<-data.frame(address=character(),lat=numeric(),long=numeric(),EID=numeric())
for(myStreet in myStreets){
requestUrl<-paste(
"http://where.yahooapis.com/geocode?appid=",appid,"&line1=",
URLencode(myStreet),
"&line2=Philadelphia,+PA"
,sep="")
cat("geocoding:",myStreet,"\n")
tryCatch({
xmlResult<-xmlTreeParse(requestUrl,isURL=TRUE,addAttributeNamespaces=TRUE)
geoResult<-xmlResult$doc$children$ResultSet$children$Result
if(xmlValue(geoResult[['quality']]) >= 87){
lat<-xmlValue(geoResult[['Latitude']])
long<-xmlValue(geoResult[['Longitude']])
myGeoTable<-rbind(myGeoTable,data.frame(address = myStreet, Y = lat, X = long,EID=NA))
}
}, error=function(err) {
cat("xml parsing or http error:", conditionMessage(err), "\n")
})
Sys.sleep(0.5)
}

#let's use the built-in numbering as the event id that PBSmapping wants
myGeoTable$EID<-as.numeric(rownames(myGeoTable))
myGeoTable
}