[R] converting character matrix to a dataframe

[Gabor Grothendieck]

You could do it directly like this:

structure(split(ch.mat, col(ch.mat)),
       row.names = 1:nrow(ch.mat), .Names = 1:ncol(ch.mat),
       class = "data.frame")


On 2/23/06, John M. Miyamoto <jmiyamot at u.washington.edu> wrote:
> Dear R-Help,
>    Suppose I have a character matrix, e.g.,
>
> (ch.mat <- matrix(c('a','s','*','f','w','*','k','*','*','f','i','o'),
> ncol=3))
>
> When I convert 'ch.mat' to a dataframe, the columns are converted to
> factors:
>
> (d1 <- data.frame(ch.mat))
> mode(d1[,1])
> is.factor(d1[,1])
>
> To prevent this, I can use 'I' to protect the column vectors:
>
> (d2 <- data.frame(x1 = I(ch.mat[,1]), x2 = I(ch.mat[,2]), x3 =
> I(ch.mat[,3])))
> mode(d2[,1])
> is.factor(d2[,2])
>
> but this method is cumbersome if the matrix has many columns.
> The following code is reasonably efficient even if the matrix has
> arbitrarily many columns.
>
> (d3 <- data.frame(apply(ch.mat,2,function(x) data.frame(I(x)))))
> mode(d3[,1])
> is.factor(d3[,1])
>
> Question:  Is there a more efficient method than the last one for
> converting a character matrix to a dataframe while preventing the
> automatic conversion of the column vectors to factors?
>
> John
>
> --------------------------------------------------------------------
> John Miyamoto, Dept. of Psychology, Box 351525
> University of Washington, Seattle, WA 98195-1525
> Phone 206-543-0805, Fax 206-685-3157
> Homepage http://faculty.washington.edu/jmiyamot/
>
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