[R] Way to convert data frame to matrix

Charles C. Berry cberry at tajo.ucsd.edu
Sat Jul 1 17:47:13 CEST 2006

I think this will do what you want:

dframe <- read.table("your.text.file", <other args as needed> )

mat <- tapply(dframe[,3],dframe[,1:2],c)

On Fri, 30 Jun 2006, Wade Wall wrote:

>  I have a text file that I have imported into R.  It contains 3 columns and
> 316940 rows.  The first column is vegetation plot ID, the second species
> names and the third is a cover value (numeric).  I imported using the
> read.table function.
> My problem is this.  I need to reformat the information as a matrix, with
> the first column becoming the row labels and the second the column labels
> and the cover values as the matrix cell data.  However, since the
> read.tablefunction imported the data as an indexed data frame, I can't
> use the columns
> as vectors.  Is there a way around this, to convert the data frame as 3
> separate vectors?  I have been looking all over for a function, and my
> programming skills are not great.
> Thanks in advance
> 	[[alternative HTML version deleted]]
>    [ Part 3.23: "Included Message" ]

Charles C. Berry                        (858) 534-2098
                                          Dept of Family/Preventive Medicine
E mailto:cberry at tajo.ucsd.edu	         UC San Diego
http://biostat.ucsd.edu/~cberry/         La Jolla, San Diego 92093-0717

More information about the R-help mailing list