library(quantmod)
start<-as.Date("2016-01-01")
end<-as.Date("2017-03-27")
getSymbols("AAPL",src="yahoo",from=start,to=end)
class(AAPL)
head(AAPL)
tail(AAPL)
plot(AAPL[,"AAPL.Close"],main="AAPL")
candleChart(AAPL, up.col="red", dn.col="blue",theme="white")

# two stock prices
getSymbols(c("MSFT","GOOG"),src="yahoo",from=start,to=end)
stocks<-as.xts(data.frame(AAPL=AAPL[,"AAPL.Close"],MSFT=MSFT[,"MSFT.Close"],
                          GOOG=GOOG[,"GOOG.Close"]))
head(stocks)
plot(as.zoo(stocks),screens=1, lty=1:3, xlab="Date",ylab="Price")
legend("right",c("AAPL","MSFT","GOOG"),lty=1:3,cex=0.5)

plot(as.zoo(stocks[,c("AAPL.Close","MSFT.Close")]), screens=1, lty=1:2,
     xlab="Date",ylab="Price")
par(new=TRUE)
plot(as.zoo(stocks[,"GOOG.Close"]),screens=1, lty=3,xaxt="n",yaxt="n",
     xlab="", ylab="")
axis(4)
mtext("Price",side=4, line=3)
legend("topleft",c("AAPL (left)","MSFT (left)","GOOG"), lty=1:3,cex=.5)