[datatable-help] v1.5.3 has just been pushed to CRAN

[Matthew Dowle]

NEW FEATURES

   o    .SD no longer includes 'by' columns, FR#978. This resolves
        the long standing annoyance of duplicated 'by' columns
        when the j expression returns a subset of rows from .SD. 
        For example, the following query no longer contains
        a redundant 'colA.1' duplicate.
            DT[,.SD[2],by=colA] #  2nd row of each group
        Any existing code that uses .SD may require simple
        changes to remove workarounds.

   o    'by' may now be a character vector of column names.
        This allows syntax such as DT[,sum(x),by=key(DT)].

   o    X[Y] now includes Y's non-join columns, as most users
        naturally expect, FR#746. Please do use j in one step
        (i.e. X[Y,j]) since that merges just the columns j uses and
        is much more efficient than X[Y][,j] or merge(X,Y)[,j].

   o    The 'Join Inherited Scope' feature is back on, FR#1095. This
        is consistent with X[Y] including Y's non-join columns, enabling
        natural progression from X[Y] to X[Y,j]. j sees columns in X
        first then Y. 
        If the same column name exists in both X and Y, the data in
        Y can be accessed via a prefix "i." (not yet implemented).

   o    Ad hoc by now coerces double to integer (provided they are
        all.equal) and character to factor, FR#1051, as setkey
        already does.

USER-VISIBLE CHANGES

   o    The default for mult is now "all", as planned and
        prior notice given in FAQ 2.2.

   o    ?[.data.table has been merged into ?data.table and updated,
        simplified, corrected and formatted.

DEPRECATED & DEFUNCT

   o    The DT() alias is now fully deprecated, as warned
        in NEWS for v1.4, and FAQs 2.6 and 2.7.