#'@title Calculate the Rolling Economic Drawdown
#'
#'@description
#'\code{rollDrawdown} calculates the Rolling Economic Drawdown(REDD) for
#'a return series.To calculate the rolling economic drawdown cumulative
#'return and rolling economic max is calculated for each point. The risk
#'free return(rf) and the lookback period(h) is taken as the input.
#'
#'Rolling Economic Drawdown is given by the equation
#'
#'\deqn{REDD(t,h)=1-\frac{W_t}/{REM(t,H)}}
#'
#'Here REM stands for Rolling Economic Max and is the code \code{\link{rollEconomicMax}}
#'
#'
#'@param R an xts, vector, matrix, data frame, timeseries, or zoo object of asset return.
#'@param Rf risk free rate can be vector such as government security rate of return
#'@param h lookback period
#'@param geometric utilize geometric chaining (TRUE) or simple/arithmetic chaining(FALSE)
#'to aggregate returns, default is TRUE
#'@param \dots any other variable
#'@author Pulkit Mehrotra
#'@seealso \code{\link{chart.REDD}} \code{\link{EconomicDrawdown}}
#'\code{\link{EDDCOPS}} \code{\link{REDDCOPS}} \code{\link{rollEconomicMax}}
#'@references Yang, Z. George and Zhong, Liang, Optimal Portfolio Strategy to
#'Control Maximum Drawdown - The Case of Risk Based Dynamic Asset Allocation (February 25, 2012)
#'@examples
#'data(edhec)
#'rollDrawdown(edhec,0.08,100)
#'data(managers)
#'rollDrawdown(managers[,1:9],managers[,10],10)
#' @export
rollDrawdown<-function(R,Rf,h, geometric = TRUE,...)
{
# DESCRIPTION:
# calculates the Rolling Economic Drawdown(REDD) for
# a return series.To calculate the rolling economic drawdown cumulative
# return and rolling economic max is calculated for each point. The risk
# free return(rf) and the lookback period(h) is taken as the input.
# FUNCTION:
x = checkData(R)
columns = ncol(x)
n = nrow(x)
columnnames = colnames(x)
rf = checkData(Rf)
nr = length(Rf)
if(nr != 1 && nr != n ){
stop("The number of rows of the returns and the risk free rate do not match")
}
index = NULL
# ERROR Handling for cases in which lookback period is greater than the number of rows
for(i in 1:ncol(x)){
if(length(na.omit(x[,i]))<h){
warning(paste("The lookback Period greater than rows eliminating series",columnnames[i]))
index = c(index,i)
columns = columns -1
}
}
if(!is.null(index)){
x = x[,-index]
columnnames = columnnames[-index]
}
REDD<-function(xh,geometric){
if(geometric)
Return.cumulative = cumprod(1+xh)
else Return.cumulative = 1 + cumsum(xh)
l = length(Return.cumulative)
if(nr == 1){
REM = max(Return.cumulative*(1+rf)^(l-c(1:l)))
}
else{
rf = rf[index(xh)]
prodRf = cumprod(1+rf)
REM = max(Return.cumulative*as.numeric(last(prodRf)/prodRf))
}
#as.numeric(first(prodRf[index(xh[which(xh==max(xh))])]))
result = 1 - last(Return.cumulative)/REM
}
for(column in 1:columns){
column.drawdown <- apply.rolling(x[,column],width = h, FUN = REDD, geometric = geometric)
if(column == 1)
rolldrawdown = column.drawdown
else rolldrawdown = merge(rolldrawdown, column.drawdown)
}
colnames(rolldrawdown) = columnnames
rolldrawdown = reclass(rolldrawdown, x)
return(rolldrawdown)
}
###############################################################################
# R (http://r-project.org/) Econometrics for Performance and Risk Analysis
#
# Copyright (c) 2004-2014 Peter Carl and Brian G. Peterson
#
# This R package is distributed under the terms of the GNU Public License (GPL)
# for full details see the file COPYING
#
# $Id: redd.R $
#
##############################################################################
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