\name{colMeans}
\alias{colMeans}
\title{Means of columns}
\arguments{
  \item{x}{DataFrame}

  \item{na.rm}{logical}

  \item{dims}{integer}
}
\description{
  Calculate means of columns of a DataFrame as if it were a
  matrix. Allow colmeans in rangeSampleMeans for DataTable
  just like a real matrix. I'm sure there is much more
  clever way to do this using aggregate.
}
\examples{
df.ds = DataFrame( a = Rle(c(5,4,3),c(2,2,2)), b = Rle(c(3,6,9),c(1,1,4)) )
 mat.ds = matrix( c(5,5,4,4,3,3,3,6,9,9,9,9), ncol=2, dimnames=list(NULL,c("a","b")))
 \dontrun{ identical( colMeans(df.ds), colMeans(mat.ds) ) }
}
\author{
  Peter M. Haverty
}