Hello,
Try the following.
dat <- read.table(text="
date y
1 2010-09-27 1356
2 2010-10-04 1968
3 2010-10-11 2602
4 2010-10-17 3116
5 2010-10-24 3496
6 2010-10-31 3958
", header=TRUE, stringsAsFactors=FALSE)
dat$date <- as.Date(dat$date)
str(dat)
search <- as.Date("2010-10-06")
max(which(dat$date <= search))
dat$y[ix]
Hope this helps,
Rui Barradas
Em 19-07-2012 08:42, Robert Latest escreveu:
Hello all,
I have a dataframe that looks like this:
head(df)
date y
1 2010-09-27 1356
2 2010-10-04 1968
3 2010-10-11 2602
4 2010-10-17 3116
5 2010-10-24 3496
6 2010-10-31 3958
I need a function that, given any date, returns the y value
corresponding to the given date or the last day before the given date.
Example:
Input: as.Date("2010-10-06"). Output: 1968 (because the last value is
from 2010-10-04)
I've been tinkering with this for an hour now, without success. I
think the solution is either surprisingly complicated or surprisingly
simple.
Thanks,
robert
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