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Revision de1c8e88aa3207bb57350371d2db8b6eaf51309c authored by Adrian Barnett on 03 August 2012, 00:00:00 UTC, committed by Gabor Csardi on 03 August 2012, 00:00:00 UTC 
version 0.3-2
1 parent 701555c
Raw File
yrfraction.R 
# yrfraction.R
# fraction of the year for a date, includes leap year
# type = 'monthly' or 'daily' (default)
# April 2009

yrfraction<-function(date,type='daily'){
  if (type=='daily'){
    if (class(date)!="Date"){stop("Date variable for annual data must be in date format, see ?Dates")} 
    year<-as.numeric(format(date,'%Y'));
    lastday<-ISOdate(year,12,31); # last day in December
    day<-as.numeric(format(date,'%j')); # Day of year as decimal number (001-366)
    yrlength<-as.numeric(format(lastday,'%j'));
    yrfrac<-(day-1)/yrlength;
  }
  if (type=='monthly'){
    if (max(date)>12|min(date)<1){stop("Date variable for monthly data must be month integer (1 to 12)")} 
    yrfrac<-(date-1)/12;
  }
  return(yrfrac)
}
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