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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>In ?data.table<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>“j is evaluated within the frame of the data.table (i.e. it sees column names as if they are variables). The result is returned. list() may be omitted when there is just one expression, for convenience.”<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I think these used to be identical (?), but now one returns a vector and the other a data.table. <o:p></o:p></p></div></body></html>