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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>Is the second result by design? I found it confusing:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>x<-data.table(a=c(1:5,1:5),b=1:10)<o:p></o:p></p><p class=MsoNormal>sum(duplicated(x)) # 0, as expected<o:p></o:p></p><p class=MsoNormal>setkey(x,a)<o:p></o:p></p><p class=MsoNormal>sum(duplicated(x)) # 5<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Thanks,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Joe<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Joseph G. Voelkel, Ph.D.<o:p></o:p></p><p class=MsoNormal>Graduate Program Chair, Center for Quality and Applied Statistics<o:p></o:p></p><p class=MsoNormal>Kate Gleason College of Engineering<o:p></o:p></p><p class=MsoNormal>Rochester Institute of Technology<o:p></o:p></p><p class=MsoNormal>V 585-475-2231<o:p></o:p></p><p class=MsoNormal>F 585-475-5959<o:p></o:p></p><p class=MsoNormal>joseph.voelkel@rit.edu<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><b><span style='font-size:10.0pt'>CONFIDENTIALITY NOTE</span></b><span style='font-size:10.0pt'>: The information transmitted, including attachments, is intended only for the person(s) or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon this information by persons or entities other than the intended recipient is prohibited. If you received this in error, please contact the sender and destroy any copies of this information.</span><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>