1- or 2-dimensional dataset in which the column(s) will be converted. A
1-dimensional dataset is considered to be a single, unnamed column.
column.spec
logical, integer, or character (name-matching) vector specifying the column(s)
of
target which is/are to be converted. To specify all columns of
target,
use "@ALL" or ""; to specify the last column of
target, use "@END"
or
"". For 2-dimensional non-matrices, specifying non-existent column(s)
will result in appending
column.spec column(s) to
target; to specify the
last column of
target plus one, use a character value not matching any of the
column names of
target; in that case,
column.spec will be used for the
name(s) of the appended column(s). For matrices,
column.spec must be "@ALL"
or
"".
column.type
character value specifying the data type to which the converted column(s) will
be coerced. Valid values are
"dates", or anything for which
paste("as", column.type, sep=".") exists.