Closest date in a vector to a given date

Question

I would like to identify the closest date in a vector of given date. Let's say I have the following date vector (with 5 random dates):

coldate= as.Date(c("2013-08-03", "2013-09-04", "2013-09-08", "2013-09-12", "2013-11-01"));

Now, I want to find the closest date to x = as.Date("2013-10-01") inside this vector.

Here is my code :

> which((coldate-x) == min(coldate-x))
  [1] 1

The result should be 4, since the date "2013-09-12" is the closest. But, I have 1... What's wrong in my code?

check `neardate` in the survival package – Tony Ladson Jun 16 '17 at 03:49 — Tony Ladson, Jun 16 '17 at 03:49
You can also use `base::findInterval(x, coldate)` – psychonomics Jan 29 '19 at 17:27 — psychonomics, Jan 29 '19 at 17:27

score 30 · Accepted Answer · answered Feb 28 '13 at 11:05

30

you miss an abs to take care of negative values:

which(abs(coldate-x) == min(abs(coldate - x)))
[1] 4

answered Feb 28 '13 at 11:05

Arun

in my actual coldate vector, I have a NA. The command is now returning integer(0). How do I have to deal with this NA ? – Henri Feb 28 '13 at 11:33
4

@Henri - remove the NA's from the `min` function: `which(abs(coldate-x) == min(abs(coldate-x),na.rm=TRUE))` – thelatemail Feb 28 '13 at 11:38
1

how would this work if x was a column of dates instead of single value? – Garglesoap May 22 '20 at 02:34

score 9 · Answer 2 · answered Feb 28 '13 at 12:49

9

See also the which.min function:

R> which.min(abs(x-coldate))
[1] 4

answered Feb 28 '13 at 12:49

rcs

1

While `which.min` seems like the obvious choice, the advantage of the answer by @Arun is that it will return multiple values if there are multiple minimum values. How you deal with those cases might actually be an issue in making a clean dataset, but it is something that should be considered. – thelatemail Feb 28 '13 at 22:08
Thanks for your comment @thelatemail. Now I sort coldate before using `which.min` to get the 'lower' match. – Stefan Jelkovich Dec 28 '20 at 21:06

score 7 · Answer 3 · answered Feb 26 '16 at 17:03

7

The which.closest() function from the birk package is a simple option.

coldate= as.Date(c("2013-08-03", "2013-09-04", "2013-09-08", "2013-09-12", "2013-11-01"))
x = as.Date("2013-10-01")

which.closest(coldate, x)
[1] 4

answered Feb 26 '16 at 17:03

CephBirk

3 Answers3