R help - Oct 2011 - Parsing variable-length delimited strings into a matrix

I'm struggling to find a way of parsing a vector of data in this sort of
form:

A,B,C
B,B
A,AA,C
A,B,BB,BBB,B,B

into a matrix (or data frame). The catch is that I don't know a priori how
many entries there will be in each element, nor how many characters there will
be. strsplit(vec,",") gets me a list, but I can't find a way of
turning the list into a matrix. unlistlst) destroys the length data and
do.call("rbind", lst) fails because of the uneven lengths. It is
possible to go through the vector element by element, but that has proved too
slow for my purposes.

Is there a reasonably quick method of achieving this in a vector-oriented way?

Cheers,

Ben

	[[alternative HTML version deleted]]

Well how do you want it be made into a matrix if the rows are all
different lengths? Methinks you are finding this tricky for a
reason...

Michael

On Mon, Oct 3, 2011 at 11:40 AM, Benjamin Wright <bjw78 at well.ox.ac.uk>
wrote:
>
> I'm struggling to find a way of parsing a vector of data in this sort
of form:
>
> A,B,C
> B,B
> A,AA,C
> A,B,BB,BBB,B,B
>
> into a matrix (or data frame). The catch is that I don't know a priori
how many entries there will be in each element, nor how many characters there
will be. strsplit(vec,",") gets me a list, but I can't find a way
of turning the list into a matrix. unlistlst) destroys the length data and
do.call("rbind", lst) fails because of the uneven lengths. It is
possible to go through the vector element by element, but that has proved too
slow for my purposes.
>
> Is there a reasonably quick method of achieving this in a vector-oriented
way?
>
> Cheers,
>
> Ben
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
> 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.
>

Will this do it for you:
> x <- readLines(textConnection("A,B,C
+ B,B
+ A,AA,C
+ A,B,BB,BBB,B,B"))
> closeAllConnections()
> x.s <- strsplit(x, ',')
> # determine max length
> x.max <- max(sapply(x.s, length))
> # create character matrix
> x.mat <- matrix(
+     sapply(x.s, function(a) c(a, rep(NA, x.max - length(a))))
+     , byrow = TRUE
+     , ncol = x.max
+     )
>
>
> x.mat
     [,1] [,2] [,3] [,4]  [,5] [,6]
[1,] "A"  "B"  "C"  NA    NA   NA
[2,] "B"  "B"  NA   NA    NA   NA
[3,] "A"  "AA" "C"  NA    NA   NA
[4,] "A"  "B"  "BB" "BBB" "B" 
"B"
>

On Mon, Oct 3, 2011 at 11:40 AM, Benjamin Wright <bjw78 at well.ox.ac.uk>
wrote:
>
> I'm struggling to find a way of parsing a vector of data in this sort
of form:
>
> A,B,C
> B,B
> A,AA,C
> A,B,BB,BBB,B,B
>
> into a matrix (or data frame). The catch is that I don't know a priori
how many entries there will be in each element, nor how many characters there
will be. strsplit(vec,",") gets me a list, but I can't find a way
of turning the list into a matrix. unlistlst) destroys the length data and
do.call("rbind", lst) fails because of the uneven lengths. It is
possible to go through the vector element by element, but that has proved too
slow for my purposes.
>
> Is there a reasonably quick method of achieving this in a vector-oriented
way?
>
> Cheers,
>
> Ben
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
> 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.
>


-- 
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?