<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px; color: rgba(0,0,0,1.0); margin: 0px; line-height: auto;">I found this behavior during a debugging session: </div><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px; color: rgba(0,0,0,1.0); margin: 0px; line-height: auto;"><br></div><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px; color: rgba(0,0,0,1.0); margin: 0px; line-height: auto;"><div id="bloop_customfont" style="margin: 0px;">> d = data.table(a=1, b=2, c=3)</div><div id="bloop_customfont" style="margin: 0px;">> setnames(d, "a", "b")</div><div id="bloop_customfont" style="margin: 0px;">> d</div><div id="bloop_customfont" style="margin: 0px;"> b b c</div><div id="bloop_customfont" style="margin: 0px;">1: 1 2 3</div><div id="bloop_customfont" style="margin: 0px;"><br></div><div id="bloop_customfont" style="margin: 0px;">Shouldn’t setnames() check if the new column names already exist before renaming, and signal an error or at least a warning if they do?</div></div><br><div id="bloop_sign_1383342346022473984"><span style="font-family:helvetica,arial;font-size:13px"></span><div style="font-family: Helvetica; line-height: normal; ">-- </div><div style="font-family: Helvetica; line-height: normal; "><span style="font-family: arial; font-size: small; ">Alexandre Sieira</span><br style="font-family: arial; font-size: small; "><span style="font-family: arial; font-size: small; ">CISA, CISSP, ISO 27001 Lead Auditor</span><br style="font-family: arial; font-size: small; "><br style="font-family: arial; font-size: small; "><span style="font-family: arial; font-size: small; ">"The truth is rarely pure and never simple."</span><br style="font-family: arial; font-size: small; "><span style="font-family: arial; font-size: small; ">Oscar Wilde, The Importance of Being Earnest, 1895, Act I</span></div></div></body></html>