Re: [R] String manipulation with regexpr, got to be a better way
Hi Chris,
why not using routines for dates
dates <- c("09/10/2003", "10/22/2005")
format(strptime(dates,format="%m/%d/%Y"),"%Y")
or take just the last 4 chars from dates
gsub(".*([0-9]{4})$","\\1",dates)
cheers
Am 29.09.2011 16:23, schrieb Chris Conner:
> Help-Rs,
>
> I'm doing some string manipulation in a file where I converted a string date
> in mm/dd/ format and returned the date .
>
> I've used regexpr (hat tip to Gabor G for a very nice earlier post on this
> function) in steps (I've un-nested the code and provided it and an example of
> what I did below. My question is: is there a more efficient way to do this.
> Specifically is there a way to use regexpr or some other string function to
> return not the first instance, but the 2nd (or for that matter 3rd, 4th or
> 5th instance) of a certain string?
>
> #first find the first occurence of "/" and create a variable for this
> firstslash <- unlist(regexpr("/", dates, fixed = TRUE)) #then use frist/ to
> cut the string field into an intermediate variable e.g., from 1/1/2008 to
> 1/2008. step1 <- substr( dates, (firstslash + 1), nchar(dates) ) #then
> repeat steps 1 and 2...there's got to be a better way step2 <-
> unlist(regexpr("/", step1, fixed = TRUE)) #then use step2 to cut string into
> final product e.g., from 1/2008 to 2008. final <- substring(step1,step2 + 1,
> nchar(step1) )
>
> Thx!
> C
> [[alternative HTML version deleted]]
>
>
>
>
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Re: [R] String manipulation with regexpr, got to be a better way
Chris Conner wrote on 09/29/2011 09:23:02 AM:
>
> Help-Rs,
>
> I'm doing some string manipulation in a file where I converted a
> string date in mm/dd/ format and returned the date .
>
> I've used regexpr (hat tip to Gabor G for a very nice earlier post
> on this function) in steps (I've un-nested the code and provided it
> and an example of what I did below. My question is: is there a more
> efficient way to do this. Specifically is there a way to use
> regexpr or some other string function to return not the first
> instance, but the 2nd (or for that matter 3rd, 4th or 5th instance)
> of a certain string?
>
> #first find the first occurence of "/" and create a variable for
> this firstslash <- unlist(regexpr("/", dates, fixed = TRUE)) #then
> use frist/ to cut the string field into an intermediate variable
> e.g., from 1/1/2008 to 1/2008. step1 <- substr( dates, (firstslash
> + 1), nchar(dates) ) #then repeat steps 1 and 2...there's got to be
> a better way step2 <- unlist(regexpr("/", step1, fixed = TRUE))
> #then use step2 to cut string into final product e.g., from 1/2008
> to 2008. final <- substring(step1,step2 + 1, nchar(step1) )
>
> Thx!
> C
# a couple example dates
dates <- c("09/10/2003", "10/22/2005")
# split the dates
dates.split <- strsplit(dates, "/")
# extract the years
sapply(dates.split, "[", 3)
Jean
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[R] String manipulation with regexpr, got to be a better way
Help-Rs,
I'm doing some string manipulation in a file where I converted a string date in
mm/dd/ format and returned the date .
I've used regexpr (hat tip to Gabor G for a very nice earlier post on this
function) in steps (I've un-nested the code and provided it and an example of
what I did below. My question is: is there a more efficient way to do this.
Specifically is there a way to use regexpr or some other string function to
return not the first instance, but the 2nd (or for that matter 3rd, 4th or 5th
instance) of a certain string?
#first find the first occurence of "/" and create a variable for this
firstslash <- unlist(regexpr("/", dates, fixed = TRUE)) #then use frist/ to cut
the string field into an intermediate variable e.g., from 1/1/2008 to 1/2008.
step1 <- substr( dates, (firstslash + 1), nchar(dates) ) #then repeat steps 1
and 2...there's got to be a better way step2 <- unlist(regexpr("/", step1,
fixed = TRUE)) #then use step2 to cut string into final product e.g., from
1/2008 to 2008. final <- substring(step1,step2 + 1, nchar(step1) )
Thx!
C
[[alternative HTML version deleted]]
__
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
