Is there a neat R trick for this?

-----Original Message-----
From: Jeff Newmiller [mailto:jdnewmil at dcn.davis.CA.us]
Sent: Tuesday, February 12, 2013 11:37 AM
To: Nordlund, Dan (DSHS/RDA); r-help at r-project.org
Subject: Re: [R] Is there a neat R trick for this?

but that doesn't maintain the sequence of the original data.
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Sent from my phone. Please excuse my brevity.

"Nordlund, Dan (DSHS/RDA)" <NordlDJ at dshs.wa.gov> wrote:

Another option is

which(y %in% x)


Dan

Daniel J. Nordlund
Washington State Department of Social and Health Services
Planning, Performance, and Accountability
Research and Data Analysis Division
Olympia, WA 98504-5204

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
project.org] On Behalf Of Pascal Oettli
Sent: Tuesday, February 12, 2013 2:21 AM
To: Robert Latest
Cc: r-help at r-project.org
Subject: Re: [R] Is there a neat R trick for this?

Hello,

?match

 > x <- c(4,5,6)
 > y <- c(10,1,5,12,4,13,14)
 > match(x,y)

[1]  5  3 NA

Hope this helps,
Pascal


Le 12/02/2013 19:09, Robert Latest a ?crit :

Hello all,

given two vectors X and Y I'd like to receive a vector Z which
contains, for each element of X, the index of the corresponding
element in Y (or NA if that element isn't in Y).

Example:

x <- c(4,5,6)
y <- c(10,1,5,12,4,13,14)

z <- findIndexIn(x, y)
z
[1] 5 3 NA

1st element of z is 5, because the 1st element of x is at the 5th

position in y

2nd element of z is 3, because the 2nd element of x is at the 3rd

position in y

3rd element of z is NA, because the 3rd element of x is not in y

Of course I can write the function findIndexIn() using a for loop,

but

in 80% of cases when I felt the urge to use "for" in R it turned

out

that there was already some builtin operator or function that did

the

trick.

Suggestions, anyone?
Thanks,

robert

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