[R] Finding the last value before a certain date

[Rui Barradas]

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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