Re: [R] Finding elements in a character vector

From: Downey, Patrick <PDowney_at_urban.org>
Date: Fri, 08 Apr 2011 20:05:44 -0400

Perfect. Thank you.

-Mitch

-----Original Message-----
From: Phil Spector [mailto:spector_at_stat.berkeley.edu] Sent: Friday, April 08, 2011 8:03 PM
To: Downey, Patrick
Cc: r-help_at_r-project.org
Subject: Re: [R] Finding elements in a character vector

match(list.a,list.b)

On Fri, 8 Apr 2011, Downey, Patrick wrote:

> Hello,
>
> I have two character vectors: list.a and list.b. Every element of
> list.a appears somewhere in list.b. Not all elements of list.b are in
> list.a, and some elements of list.b appear multiple times in list.a. I
> want to create a new vector (index) of the same length as list.a where
> the nth element of index is the location in list.b of the nth element of
list.a.
>
> This code will work, but I have heard over and over again that using
> loops is inefficient in R and that there are (almost always) better
> ways to do things.
>
> for(i in 1:length(list.a)){
> index[i] <- seq(1,length(list.b))[list.b==list.a[i]]
> }
>
> Thank you,
> Mitch
>
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>



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