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by Joseph Rickert

The weather is on everybody's mind these days: too much ice and snow east of the Rockies and no rain to speak fo in California. Ram Narasimhan has made it a little easier for R users to keep track of what's going on and also get a historical perspective. His new R package weatherData makes it easy to down load weather data from various stations around the world collecting data.  Here is a time series plot of the average temperature recorded at SFO last year with the help of the weatherData's getWeatherForYear() function. It is really nice that the function returns a data frame of hourly data with the Time variable as class POSIXct.

### Some Code to Get Average Temperature at SFO
# JB Rickert
library(weatherData)
library(ggplot2)
library(scales)
library(plyr)

w2013 <- getWeatherForYear("sfo",2013)

w2013$shortdate <- strftime(w2013$Time, format="%m-%d")

meanTemp <- ddply(w2013, .(shortdate), summarize, mean_T=mean(TemperatureF))
meanTemp$shortdate <- as.Date(meanTemp$shortdate,format="%m-%d")

ggplot(meanTemp, aes(shortdate, mean_T)) + geom_line() +
scale_x_date(labels=date_format("%m/%d")) + xlab("") + ylab("Mean Temp deg F") +
ggtitle("2013 Average Daily Temperature at SFO")