how to avoid loops & using xts, quantmod

Hey all,

I'm struggling with my first lines of R code.
It would be great if someone could help me to get the code
below runing, or show me how to do this task more efficient.

- can I avoid to use the loops?
- why does "Lo(GDAXI[i]) < tmp.lowest" not return a boolean?

best regards
Immanuel

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# clear workspace
rm(list = ls())
# set working directory
setwd("~/Ue1")

# load libraries
library(quantmod)
library(TTR)

# load costum functions
source("A2_func.R")

underlying = "GDAXI"

getSymbols("^GDAXI")
# trendfilter: -1 down-trend, 1 up-trend
# nothing smart, just an xts object containing 1 & -1
# according to trendfilter
direction = dir.macd(GDAXI)

period.lowest = xts(Inf, Sys.Date())
period.highest = xts(-Inf, Sys.Date())
tmp.lowest <- xts(Inf , Sys.Date()) # max value nehmen...
tmp.highest <- xts(-Inf, Sys.Date())
# now i want to find the max value (increasing) for every 
up-trend-periode (1,1,1)
# and min value for every down-trend-periode (decreasing) (-1,-1,-1)
for ( i in 1 : length(direction) ) {

    if (direction[i] == -1)    {
        tmp.highest <- -Inf
        if ( Lo(GDAXI[i]) < tmp.lowest)
            period.lowest[i] <- tmp.lowest
    }
    if (direction[i] == 1)    {
        tmp.lowest <- Inf
        if (Hi(GDAXI[i] > tmp.highest)
            period.highest <- tmp.highest
    }

}

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dir.macd <- function(priceSeries) {
    library(quantmod)
    library(TTR)
    # MACD settings
    slow = 10
    fast = 25
    av = 5

    # Calculate the MACD indicator
    macd <- MACD(priceSeries, fast,slow,av )

    # Create the long (up) and short (dn) signals
    sigup <- ifelse(macd$macd < macd$signal, 1, 0)
    sigdn <- ifelse(macd$macd > macd$signal, -1, 0)

    # Lag signals to align with days in market,
    # not days signals were generated
    #sigup <- Lag(sigup,1) # Use lag() to avoid Toby's error
    #sigdn <- Lag(sigdn,1) # Use lag() to avoid Toby's error
    sigup <- lag(sigup,1) # Note k=1 implies a move *forward*
    sigdn <- lag(sigdn,1) # Note k=1 implies a move *forward*

    # Replace missing signals with no position
    # (generally just at beginning of series)
    sigup[is.na(sigup)] <- 0
    sigdn[is.na(sigdn)] <- 0

    # Combine both signals into one vector
    sig <- sigup + sigdn

    # Calculate SAR-direction
    for ( i in 2 : length(sig) ) {
        if (sig[i] == 0)
            sig[i]=sig[i-1]
    }
    sig
}
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