Created
November 16, 2012 11:05
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RealClearPolitics XML Scraping
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doInstall <- TRUE # Change to FALSE if you don't want packages installed. | |
toInstall <- c("XML", "ggplot2", "lubridate", "reshape2", "scales") | |
if(doInstall){install.packages(toInstall, repos = "http://cran.r-project.org")} | |
lapply(toInstall, library, character.only = TRUE) | |
# Find your XML file from those listed at | |
# http://cdn.realclearpolitics.com/epolls/charts/ | |
URL <- "http://cdn.realclearpolitics.com/epolls/charts/1171.xml" | |
parsedXML <- xmlParse(URL) # First pass | |
dateSeries <- xpathSApply(parsedXML, path = "//series") # Check the structure | |
Date <- sapply(xmlChildren(dateSeries[[1]]), xmlValue) # of the XML. <series> | |
names(Date) <- sapply(xmlChildren(dateSeries[[1]]), # is the first child node. | |
xmlGetAttr, "xid") | |
graphSeries <- xpathSApply(parsedXML, path = "//graph") # <graph> is the | |
obamaSeries <- sapply(xmlChildren(graphSeries[[1]]), xmlValue) # second major | |
names(obamaSeries) <- sapply(xmlChildren(graphSeries[[1]]), # child node. | |
xmlGetAttr, "xid") # ^ The first graph line | |
romneySeries <- sapply(xmlChildren(graphSeries[[2]]), xmlValue) # is "Obama" | |
names(romneySeries) <- sapply(xmlChildren(graphSeries[[2]]), # The second | |
xmlGetAttr, "xid") # ^ is "Romney." | |
# Put all of these series into a data.frame | |
rcpData <- data.frame(xid = names(Date), stringsAsFactors = FALSE) | |
rcpData$Date <- mdy(Date[rcpData$xid], tz = "EST") # lubridate! | |
rcpData$Romney <- as.numeric(romneySeries[rcpData$xid]) | |
rcpData$Obama <- as.numeric(obamaSeries[rcpData$xid]) | |
write.csv(rcpData, "RealClearPolitics Polling Average.csv", row.names = F) |
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RCP does not make the XMLs visible in the source anymore. Any idea how this can be updated to reflect this, including a new way of sniffing the XLMs? Or did they switch to other storage solution (json?)