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# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Library General Public
# License as published by the Free Software Foundation; either
# version 2 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR Description. See the
# GNU Library General Public License for more details.
#
# You should have received a copy of the GNU Library General
# Public License along with this library; if not, write to the
# Free Foundation, Inc., 59 Temple Place, Suite 330, Boston,
# MA 02111-1307 USA
# Copyrights (C)
# for this R-port:
# 1999 - Diethelm Wuertz, GPL
# 2007 - Rmetrics Foundation, GPL
# Diethelm Wuertz <wuertz@itp.phys.ethz.ch>
# for code accessed (or partly included) from other sources:
# see Rmetric's copyright and license files
################################################################################
# FUNCTION: DESCRIPTION:
# equidistWindows Defines default equal distant rolling windows
# tangencyStrategy Defines default tangency strategy portfolio
# emaSmoother Defines default EMA weights smoother
################################################################################
equidistWindows <-
function(data, backtest = portfolioBacktest())
{
# A function implemented by Diethelm Wuertz and William Chen
# Description:
# Defines default equidistant rolling windows
# Arguments:
# data - portfolio assets set, an object of class 'timeSeries'
# backtest - an object of class 'fPFOLIOBACKTEST'
# Note:
# This is an example for a user defined windows function ...
# Example:
# equidistWindows(as.timeSeries(data(LPP2005REC)))
# FUNCTION:
# Settings:
horizon = getWindowsHorizon(backtest)
# Rolling Windows:
ans = rollingWindows(x = data, period = horizon, by = "1m")
# Return Value:
ans
}
# ------------------------------------------------------------------------------
tangencyStrategy <-
function(data, spec = portfolioSpec(), constraints = "LongOnly",
backtest = portfolioBacktest())
{
# A function implemented by Diethelm Wuertz and William Chen
# FUNCTION:
# Strategy Portfolio:
strategyPortfolio <- try(tangencyPortfolio(data, spec, constraints))
# If tangency portfolio doesn't exist take the minimum variance portfolio:
if (class(strategyPortfolio) == "try-error") {
strategyPortfolio <- minvariancePortfolio(data, spec, constraints)
}
# Return Value:
strategyPortfolio
}
# ------------------------------------------------------------------------------
emaSmoother <-
function(weights, spec, backtest)
{
# A function implemented by Diethelm Wuertz and William Chen
# Description:
# A user defined weights smoother for portfolio backtesting
# Arguments:
# weights - a numeric matrix of weights
# spec - portfolio spec, an object of class fPFLOLIOSPEC
# backtest - portfolio backtest, an object of class fPFLOLIOBACKTEST
# Example:
# ans = portfolioBacktesting( ... )
# emaSmoother(ans$weights, spec, backtest)
# FUNCTION:
# EMA Function:
ema <- function (x, lambda) {
x = as.vector(x)
lambda = 2/(lambda + 1)
xlam = x * lambda
xlam[1] = x[1]
ema = filter(xlam, filter = (1 - lambda), method = "rec")
ema[is.na(ema)] <- 0
as.numeric(ema) }
# Lambda:
lambda = getSmootherLambda(backtest)
lambdaLength = as.numeric(substr(lambda, 1, nchar(lambda) - 1))
lambdaUnit = substr(lambda, nchar(lambda), nchar(lambda))
stopifnot(lambdaUnit == "m")
lambda = lambdaLength
# Initial Weights
nAssets = ncol(weights)
initialWeights = getSmootherInitialWeights(backtest)
if (!is.null(initialWeights)) weights[1, ] = initialWeights
# Compute Exponentially Smoothed Weights:
smoothWeights1 = NULL
for (i in 1:nAssets) {
# print("first smooth")
EMA = ema(weights[, i], lambda = lambda)
smoothWeights1 = cbind(smoothWeights1, EMA)
}
# Double Smoothing ?
doubleSmooth = getSmootherDoubleSmoothing(backtest)
if (doubleSmooth) {
# print("second smooth")
smoothWeights = NULL
for (i in 1:nAssets) {
EMA = ema(smoothWeights1[, i], lambda = lambda)
smoothWeights = cbind(smoothWeights, EMA)
}
} else {
smoothWeights = smoothWeights1
}
# Add Names:
rownames(smoothWeights) = rownames(weights)
colnames(smoothWeights) = colnames(weights)
# Return Value:
smoothWeights
}
################################################################################
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