[R] help with gsub and date pattern

[Marc Schwartz]

On May 21, 2009, at 4:13 PM, Tim Clark wrote:

>
> Dear List,
>
> I am having a problem using gsub to remove dates from a date/time  
> string.
>
> For example:
>
> x<-c("5/31/2009 12:34:00","6/1/2009 1:14:00")
>
> I would like to remove the date and have just the time.
>
> I have tried:
> gsub("[0-9+]/[0-9+]/[0-9+]","",x)
>
> and various versions.  I think my problem is that the / is a special  
> character and is telling it something that I don't mean.  I would  
> appreciate any suggestions on how to proceed.
>
> Thanks,
>
> Tim



Switch the '+' to outside the brackets:

 > gsub("[0-9]+/[0-9]+/[0-9]+ ","",x)
[1] "12:34:00" "1:14:00"


A few other options:

# Use strsplit
 > sapply(strsplit(x, split = " "), "[", 2)
[1] "12:34:00" "1:14:00"


# Return the pattern contained within the parens
# See ?regex
 > gsub("^.* (.*)$", "\\1", x)
[1] "12:34:00" "1:14:00"


# Replace the characters up to the space with an empty vector
 > gsub("^.* ", "", x)
[1] "12:34:00" "1:14:00"


HTH,

Marc Schwartz