Analyzing iPad 3 U.S. adoption based on Chitika data

# blog post: http://www.reakkt.com/2012/04/are-new-ipad-sales-slowing.html

### CHITIKA DATA
# http://labs.chitika.com/ipad/
### CODE

library(TTR)

dataN <- length(iPadNewData)
avgN  <- ceiling(dataN/10)

m <- runMean(iPadNewData,avgN)
v <- runSD(iPadNewData,avgN)

delta <- rep(NA,dataN)
for (i in (avgN*2):dataN) delta[i] <- log( m[i] / m[i-avgN+1] )

par(mfrow=c(2,1))

plot(iPadNewData,type="l",log="y",
     main="new iPad U.S. adoption (log)",
     sub="source: Chitika",
     ylab="adoption %")
lines(m,col="Red",lty="solid")
lines(m+2*v,col="Orange",lty="dotted")
lines(m-2*v,col="Orange",lty="dotted")
legend("bottomright",paste("Last AVG=",format(tail(m,1),digits=4)))

delta_positive <- rep(NA,dataN)
delta_positive[which(delta>0)] <- delta[which(delta>0)]
delta_negative <- rep(NA,dataN)
delta_negative[which(delta<0)] <- delta[which(delta<0)]

plot(delta_positive,type="h",col="Blue",
     main="average change",ylab="change",ylim=range(delta,na.rm=TRUE))
lines(delta_negative,type="h",col="Red")

par(mfrow=c(1,1))