Return closest date to a given date in R
It's a bit confusing since you use variables which you didn't include in your examples.
But I think this is what you want:
for (ii in 1:nrow(df)) df$birthseason[ii] <-as.character(season_enddates[which.min(abs(df$birthdate[ii] - season_enddates))])
Alternatively using lapply
:
df$birthseason <- unlist(lapply(df$birthdate,function(x) as.character(season_enddates[which.min(abs(x - season_enddates))])))
Result:
> df
ID birthdate birthseason
1 a 2012-06-12 2012-06-21
2 b 2014-06-14 2014-06-25
3 c 2015-11-11 2015-11-16
4 d 2016-09-30 2016-11-22
5 a 2012-06-12 2012-06-21
You are looking for which season_enddate
is the closest to birthdate[1]
, and birthdate[2]
, etc.
To get the data straight, I will create an actual reproducible example:
birthdate <- as.Date(c("2012-06-12", "2014-06-14",
"2015-11-11", "2016-09-30",
"2012-06-12"))
season_enddates <- as.Date(c("2011-11-10", "2012-11-28",
"2013-11-29", "2014-11-26",
"2015-11-16", "2016-11-22",
"2012-06-21", "2013-06-23",
"2014-06-25", "2015-06-08",
"2016-06-14"))
Basically I use the function you also used, except that I decided to break it down a bit, so it's easier to follow what you're trying to do:
new.vector <- rep(0, length(birthdate))
for(i in 1:length(birthdate)){
diffs <- abs(birthdate[i] - season_enddates)
inds <- which.min(diffs)
new.vector[i] <- season_enddates[inds]
}
# new.vector now contains some dates that have been converted to numbers:
as.Date(new.vector, origin = "1970-01-01")
# [1] "2012-06-21" "2014-06-25" "2015-11-16" "2016-11-22"
# [5] "2012-06-21"