R: Stock density plot with finance.yahoo.com as source

density-stocks.r

##Requires a data frame with column "Name" (type as.character) and "Tags"

library(tseries)
library(ggplot2)

# get all the quotes for the stocks and put it in a dataframe
get.quotes.df <- function(stocks.df, start){
	

 stock.values <- NULL

    #Download all the closing values for each stock
  for(index in 1: length(stocks.df$Tags)){
  	print(stocks.df[index,1])
	stock.prices <- get.hist.quote(stocks.df[index, 2], as.Date(start), quote=c("Close"), , , , retclass = c("zoo"))
	
	if(class(stock.values) == "NULL"){
	 stock.values <- stock.prices
	}else{
	 stock.values <- merge(stock.values, stock.prices)
	}
	
 }
    #Add stockname as column name
column.names <- c()
for(index in 1:length(stocks.df$Name)){
   column.names <- c(column.names, stocks.df[index, 1])
}

names(stock.values) <- column.names
return(stock.values)
 }

#returns a dataframe of one stock and removes the NA values
get.stock.df <- function(stock){
	stock <- stock[which(!is.na(stock))]
 	x <- 1:length(stock)
 	df <- data.frame(x, stock)
 	return(df)
}

#create a density plot of the stock values
get.stock.density <- function(stock.df){
  plot <- qplot(stock.df$stock, data=stock.df, geom='density')
}