[R] Determine all specific same dates between two given dates

[Uwe Ligges]

On 25.07.2014 18:26, Frank S. wrote:
> Hi everyone, After trying to find the solution during days, I decided to write in this help list in order to ask  if anyone can help me.I would want to construct an R function, with  "initial", "final" and "specific" dates as 3 arguments (for example, becauseI'm not really sure it is the best way), which returns a vector "v" containing all the specific same dates between the given "initial" and "final" dates (so the vector will contain only the specific date as many times as it appears inside the reference period). The function could have this aspect: myfun <- function(initial=as.Date("initial"), final=as.Date("final"),                             day_specific=day, month_specific=month)                                               { ....                     return(v)                    } Example of what I'm trying to explain: Let's say I want to obtain all the dates 25st September contained between initial="05-07-1990" and final="19-03-1998": myfun (initial=as.Date("05-07-1!
>   998"), final=as.Date("19-03-2003"),             day_specific=25, month_specific=9) The result I would expect is: v = c ("25-09-1998", "25-09-1999", "25-09-2000", "25-09-2001", "25-09-2002") Please, if somebody has any idea how to do the function, it will help me a lot. Thanks in advance!   		 	   		
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Many solutions, one may be:

myfun <- function(initial, final, day_specific, month_specific){
     v <- as.Date(paste(format(c(initial, final), "%Y"), month_specific, 
day_specific, sep="-"))
     v <- seq(v[1], v[2], by = "year")
     v[v >= initial & v <= final]
}

initial <- as.Date("05-07-1998", "%d-%m-%Y")
final <- as.Date("19-03-2003", "%d-%m-%Y")
day_specific <- 25
month_specific <- 9

myfun(initial, final, day_specific, month_specific)