R help - Apr 2011 - Creating a dataframe from a vector of character strings

I have a vector of character strings that I would like to split in two, and
place in columns of a dataframe.

So for example, I start with this:

beatles <- c("John Lennon", "Paul McCartney",
"George Harrison", "Ringo
Starr")

and I want to end up with a data frame that looks like this:
> Beatles = data.frame(firstName=c("John", "Paul",
"George", "Ringo"),
                       lastName=c("Lennon", "McCartney",
"Harrison",
"Starr"))
> Beatles
  firstName  lastName
1      John    Lennon
2      Paul McCartney
3    George  Harrison
4     Ringo     Starr


I tried string-splitting the first vector on the spaces between first and
last names, and it returned a list:
> strsplit(beatles, " ")
[[1]]
[1] "John"   "Lennon"

[[2]]
[1] "Paul"      "McCartney"

[[3]]
[1] "George"   "Harrison"

[[4]]
[1] "Ringo" "Starr"


Is there a fast way to convert this list into a data frame?  Right now all I
can think of is using a for loop, which I would like to avoid, since the
real application I am working on involves a much larger dataset.

--
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Sent from the R help mailing list archive at Nabble.com.

You could use ?unlist:

structure(data.frame(
    matrix(unlist(strsplit(beatles," ")),length(beatles),2,T)),
    names=c("FirstName","LastName"))

Note that this compact code does not guard you against typos, that is
names with >2 or <2 elements.

Hope that helps,
Denes


> I have a vector of character strings that I would like to split in two,
> and
> place in columns of a dataframe.
>
> So for example, I start with this:
>
> beatles <- c("John Lennon", "Paul McCartney",
"George Harrison", "Ringo
> Starr")
>
> and I want to end up with a data frame that looks like this:
>
>> Beatles = data.frame(firstName=c("John", "Paul",
"George", "Ringo"),
>                        lastName=c("Lennon",
"McCartney", "Harrison",
> "Starr"))
>> Beatles
>   firstName  lastName
> 1      John    Lennon
> 2      Paul McCartney
> 3    George  Harrison
> 4     Ringo     Starr
>
>
> I tried string-splitting the first vector on the spaces between first and
> last names, and it returned a list:
>
>> strsplit(beatles, " ")
> [[1]]
> [1] "John"   "Lennon"
>
> [[2]]
> [1] "Paul"      "McCartney"
>
> [[3]]
> [1] "George"   "Harrison"
>
> [[4]]
> [1] "Ringo" "Starr"
>
>
> Is there a fast way to convert this list into a data frame?  Right now all
> I
> can think of is using a for loop, which I would like to avoid, since the
> real application I am working on involves a much larger dataset.
>
> --
> View this message in context:
>
http://r.789695.n4.nabble.com/Creating-a-dataframe-from-a-vector-of-character-strings-tp3450716p3450716.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

On 15/04/11 09:04, Cliff Clive wrote:
> I have a vector of character strings that I would like to split in two, and
> place in columns of a dataframe.
>
> So for example, I start with this:
>
> beatles<- c("John Lennon", "Paul McCartney",
"George Harrison", "Ringo
> Starr")
>
> and I want to end up with a data frame that looks like this:
>
>> Beatles = data.frame(firstName=c("John", "Paul",
"George", "Ringo"),
>                         lastName=c("Lennon",
"McCartney", "Harrison",
> "Starr"))
>> Beatles
>    firstName  lastName
> 1      John    Lennon
> 2      Paul McCartney
> 3    George  Harrison
> 4     Ringo     Starr
>
>
> I tried string-splitting the first vector on the spaces between first and
> last names, and it returned a list:
>
>> strsplit(beatles, " ")
> [[1]]
> [1] "John"   "Lennon"
>
> [[2]]
> [1] "Paul"      "McCartney"
>
> [[3]]
> [1] "George"   "Harrison"
>
> [[4]]
> [1] "Ringo" "Starr"
>
>
> Is there a fast way to convert this list into a data frame?  Right now all
I
> can think of is using a for loop, which I would like to avoid, since the
> real application I am working on involves a much larger dataset
Whenever you think of using a for loop, stop and think about using
some flavour of apply() instead:

melvin <- strsplit(beatles," ")
clyde <- data.frame(firstName=sapply(melvin,function(x){x[1]}),
                                     
lastName=sapply(melvin,function(x){x[2]}))

     cheers,

             Rolf Turner

On 4/14/2011 2:04 PM, Cliff Clive wrote:
> I have a vector of character strings that I would like to split in two, and
> place in columns of a dataframe.
>
> So for example, I start with this:
>
> beatles<- c("John Lennon", "Paul McCartney",
"George Harrison", "Ringo
> Starr")
>
> and I want to end up with a data frame that looks like this:
>
>> Beatles = data.frame(firstName=c("John", "Paul",
"George", "Ringo"),
>                         lastName=c("Lennon",
"McCartney", "Harrison",
> "Starr"))
>> Beatles
>    firstName  lastName
> 1      John    Lennon
> 2      Paul McCartney
> 3    George  Harrison
> 4     Ringo     Starr
>
>
> I tried string-splitting the first vector on the spaces between first and
> last names, and it returned a list:
>
>> strsplit(beatles, " ")
> [[1]]
> [1] "John"   "Lennon"
>
> [[2]]
> [1] "Paul"      "McCartney"
>
> [[3]]
> [1] "George"   "Harrison"
>
> [[4]]
> [1] "Ringo" "Starr"
>
>
> Is there a fast way to convert this list into a data frame?  Right now all
I
> can think of is using a for loop, which I would like to avoid, since the
> real application I am working on involves a much larger dataset.
Another approach, in addition to the ones you have already been given, 
is to use the colsplit function in the reshape package.  This is the 
sort of thing it is designed to do.

library("reshape")
colsplit(beatles, " ", names=c("firstName",
"lastName"))

Similar caveats apply, though, in that it assumes only 2 names that are 
separated by one space (and will give a warning if that is not the case).

-- 
Brian S. Diggs, PhD
Senior Research Associate, Department of Surgery
Oregon Health & Science University