Michael,
Your suggestion to use sapply solves the problem.Thanks so much for your help
Mauricio
________________________________
From: R. Michael Weylandt <michael.weyla...@gmail.com>
Cc: "r-help@r-project.org" <r-help@r-project.org>
Sent: Friday, March 30, 2012 8:33 PM
Subject: Re: [R] How to use access results of gregexpr in data frames
I think when you assign to dframe$all there's more going on than you
realize: you're actually using a multi-element list as a column of a
data frame which is, while possible, perhaps nonstandard. Perhaps you
want this:
dframe$all <- t(simplify2array(gregexpr("/", dframe[, 1])))
print(dframe)
# date x1 all.1 all.2
# 1 5/14/2011 2 2 5
# 2 4/7/2011 2 2 4
If you just want the location of the second slash, this works:
dframe$x2 <- sapply(gregexpr("/", dframe[, 1]),`[`,2)
Hope this helps,
Michael
On Fri, Mar 30, 2012 at 7:14 PM, Mauricio Cornejo
> Hello,
> I'm trying to figure out how to find the index of the second occurrence of
> "/" in a string (which happens to represent a date) within a data frame
> column.
>
> I've used the following code successfully to find the first instance of "/".
>
>
> dframe <- data.frame(date=c("5/14/2011", "4/7/2011"))
> dframe$x1 <- regexpr("/", dframe[, 1])
> dframe
> date x1
> 1 5/14/2011 2
> 2 4/7/2011 2To find the second instance, I thought I'd try to use gregexpr
> to find all instances of "/" (there's always two per string).
>
>
> dframe$all <- gregexpr("/", dframe[, 1])
> dframe
> date x1 all
> 1 5/14/2011 2 2,5
> 2 4/7/2011 2 2,4
> So far so good. I then thought to index the second element of dframe$all. I
> tried both of the following unsuccessfully.
>
> dframe$x2 <- dframe[, "all"][[2]]
> dframe$x2 <- dframe[, "all"][2]
>
> The desired final output is as follows ... but I don't know how to get there.
> date x1 all x2
> 1 5/14/2011 2 2,5 5
> 2 4/7/2011 2 2,4 4
> Many thanks for your help,
> Mauricio
>
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>
>
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