R help - Sep 2009 - Rmetrics timeDate - business days between dates

Hi

One of the most important calculation in applied finance is the number of
days between dates.
That kind of calculus become annoying when a specific calendar must be used.
That is the case for the business days calculus.

The package timeDate has a function isBizday to perform that kind of thing.
The problem is that using this function to calculate the number of business
days between dates has taken a very long time. An example of such an
implementation is the function below.

Has anyone an optimized function to to this counts?

 Clearly I  have in mind to perform at least the basic analytics for a bond:
Duration, internal rate of return ,  net present value, etc... That is not
time feasible with a portfolio of bond  using the function below.

tks

library(timeDate)

BuziInDates <- function(start, end, holidays){
#calculates the number of business days
#between the dates start and end.

if(class(start) != "Date" | class(end) != "Date"){
  stop("Arguments must be of class Date.")
}

if(class(holidays) != "function"){
  stop("holidays must be a function")
}

if(start > end){
  stop("start date must not be greater than end date.")
}

y1 <- as.POSIXlt(start)$year + 1900
y2 <- as.POSIXlt(end)$year   + 1900

seqs  <- timeSequence(from = start, to = end, by = "day")

ndays <- length(seqs)

dts   <- NULL
temp  <- NULL
if( y1 == y2){
  temp  <- window(holidays(y1), start = start, end = end)
  dts   <- seqs[isBizday(seqs,temp)]
}else{
     temp <- holidays(y1)
     for(k in seq(from = y1+1, to = y2)){
        temp <- c(temp,holidays(k))
     }
     temp   <- window(temp, start = start, end = end)
     dts    <- seqs[isBizday(seqs,temp)]
}

bdays <- length(dts)

return(bdays)
}


### using the function...

BuziInDates(as.Date('2009-09-11'),  as.Date('2030-09-11') , 
holidayNYSE)

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