

   MMaattrriicceess

        matrix(data = NA, nrow = 1, ncol = 1, byrow = FALSE, dimnames = NULL)
        as.matrix(x)
        is.matrix(x)

   DDeessccrriippttiioonn::

        `matrix' creates a matrix from the given set of values.
        `nrow' gives the desired number of rows and `ncol' the
        desired number of columns.  If either of `nrow' or
        `ncol' is not given, an attempt is made to infer it
        from the length of `data' and the other parameter.  If
        `byrow' is `FALSE' (the default) the matrix is filled
        by columns, otherwise the matrix is filled by rows.  A
        `dimnames' attribute for the matrix can be specified
        with the optional `dimnames' argument (which thus has
        to be a `list' of length 2).

        `as.matrix' attempts to turn its argument into a
        matrix.  This function is generic with a default and a
        `data.frame' method.

        `is.matrix' returns `TRUE' if `x' is a matrix (i.e., it
        not a `data.frame' and has a `dim' attribute of length
        2) and `FALSE' otherwise.

   SSeeee AAllssoo::

        `data.matrix'.

   EExxaammpplleess::

        is.matrix(as.matrix(1:10))
        data(warpbreaks)
        !is.matrix(warpbreaks)# data.frame, NOT matrix!
        str(warpbreaks)
        str(as.matrix(warpbreaks))#using as.matrix.data.frame(.) method

