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/yyyy format and returned the date yyyy.
>
> 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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