Pipeline to Plot Annual % Change

(thanks tradeblotter for pointing out error in code in first release)

Pipes in R make my life incredibly easy, and I think my code easier to read.   Note, there are a couple different flavors of pipes (see magrittr and pipeR).  For now, I choose pipeR.

library(quantmod)
library(pipeR)
library(ggplot2)

getSymbols("^GSPC",from="1900-01-01",auto.assign=F) %>>% #get S&P 500 from Yahoo!Finance
  ( .[endpoints(.,"years"),4] ) %>>% #get end of year
  ROC( type="discrete", n=1 ) %>>%   #get one year rate of change
  na.fill(0) %>>%                    #fill first year with 0
  (                                  #make data.frame
    data.frame(
      date = as.Date(format(index(.),"%Y-01-01"))
      ,.
    )
  ) %>>%
  structure(                         #hard way to do colnames()
    names = c("date","change")
  ) %>>%
  ggplot(                            #start our plot pipe
    aes( y= change, x=  date)
  ) %>>%
  + geom_bar( stat="identity" ) %>>% #choose bar
  + labs( title = "Annual Change of the S&P 500" ) #give plot a title

Or if we wanted to use the new pipeline syntax for the plot portion.

library(quantmod)
library(pipeR)
library(ggplot2)

getSymbols("^GSPC",from="1900-01-01",auto.assign=F) %>>% #get S&P 500 from Yahoo!Finance
  ( .[endpoints(.,"years"),4] ) %>>% #get end of year
  ROC( type="discrete", n=1 ) %>>%   #get one year rate of change
  na.fill(0) %>>%                    #fill first year with 0
  (                                  #make data.frame
    data.frame(
      date = as.Date(format(index(.),"%Y-01-01"))
      ,.
    )
  ) %>>%
  structure(                         #hard way to do colnames()
    names = c("date","change")
  ) %>>%
  (
    pipeline({
      ggplot(., aes( y= change, x=  date) )
      + geom_bar( stat="identity" )
      + labs( title = "Annual Change of the S&P 500 (source: Yahoo! Finance)" )
    })
  )