R help - May 2009 - help with gsub and date pattern

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



Tim Clark
Department of Zoology 
University of Hawaii

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

Thanks for the help and the various options!  Putting the + outside the brackets
worked, but I like the strsplit option.  Always nice to learn new functions!

Aloha,

Tim



--- On Thu, 5/21/09, Marc Schwartz <marc_schwartz at me.com> wrote:
> From: Marc Schwartz <marc_schwartz at me.com>
> Subject: Re: [R] help with gsub and date pattern
> To: "Tim Clark" <mudiver1200 at yahoo.com>
> Cc: r-help at r-project.org
> Date: Thursday, May 21, 2009, 11:34 AM
> 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
> 
>