[R] convert a data.frame to matrix

[peter dalgaard]

On May 17, 2013, at 01:59 , David Winsemius wrote:

> 
> On May 16, 2013, at 1:46 PM, Hermann Norpois wrote:
> 
>> Hello,
>> 
>> I fail to tranfer data from a dataframe to a matrix.
>> 
>> jam is from a dataframe (and belongs still to the class dataframe) and
>> should look like m (see below).
>> 
>>> jam
>> vec1 vec3  d1  d2
>> 1  172  173 223 356
>>> dput (jam)
>> structure(list(vec1 = 172L, vec3 = 173L, d1 = 223L, d2 = 356L), .Names =
>> c("vec1",
>> "vec3", "d1", "d2"), row.names = 1L, class = "data.frame")
>>> m      #THIS IS THE AIM
>>    [,1] [,2]
>> [1,]  172  223
>> [2,]  173  356
>> 
>>> dput (m)
>> structure(c(172, 173, 223, 356), .Dim = c(2L, 2L))
>> 
>> How can I transform jam to m?
> 
> jam <- structure(list(vec1 = 172L, vec3 = 173L, d1 = 223L, d2 = 356L), .Names =
> c("vec1",
> "vec3", "d1", "d2"), row.names = 1L, class = "data.frame")
> jm <- data.matrix(jam)
> dim(jm) <- c(2,2) # re-dimension a matrix with column-major order
> jm
> 
>     [,1] [,2]
> [1,]  172  223
> [2,]  173  356

also

> matrix(unlist(jam),2)
     [,1] [,2]
[1,]  172  223
[2,]  173  356


-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com