<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><p>Gabor,</p>
<p>It's the same as in 1.8.10 and 1.9.2. What is contradicting in <code>?data.table</code>? It says under <code>.I</code>: <em>"<code>.I</code> is an integer vector length <code>.N</code> holding the row locations in <code>x</code> for this group."</em></p>
<p>The row locations in <code>x</code> for <code>b=1,2,1,2</code> are <code>1,2,3,4</code> which then becomes <code>1,3</code> and <code>2,4</code> for <em>this group</em> => <code>b=1</code> and <code>b=2</code> respectively.</p>
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.error { color:#AA0000; }</style></p><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 style="color: rgb(34, 34, 34); font-family: arial; font-size: small; "><br></div></div> <div id="bloop_sign_1396350809415343104" class="bloop_sign"><div style="font-family:helvetica,arial;font-size:13px">Arun</div></div> <div style="color:black"><br>From: <span style="color:black">Gabor Grothendieck</span> <a href="mailto:ggrothendieck@gmail.com">ggrothendieck@gmail.com</a><br>Reply: <span style="color:black">Gabor Grothendieck</span> <a href="mailto:ggrothendieck@gmail.com">ggrothendieck@gmail.com</a><br>Date: <span style="color:black">April 1, 2014 at 1:09:23 PM</span><br>To: <span style="color:black">datatable-help@lists.r-forge.r-project.org</span> <a href="mailto:datatable-help@lists.r-forge.r-project.org">datatable-help@lists.r-forge.r-project.org</a><br>Subject: <span style="color:black"> [datatable-help] .I does not respect by <br></span></div><br> <blockquote type="cite" class="clean_bq"><span><div><div></div><div>In the following .I seems not to be within group.
<br>
<br>> dt <- data.table(a = 1:4, b = 1:2)
<br>> dt[, .I, by = b]
<br> b .I
<br>1: 1 1
<br>2: 1 3
<br>3: 2 2
<br>4: 2 4
<br>> packageVersion("data.table")
<br>[1] '1.9.3'
<br>
<br>This seems contrary to ?data.table.
<br>
<br>
<br>--
<br>Statistics & Software Consulting
<br>GKX Group, GKX Associates Inc.
<br>tel: 1-877-GKX-GROUP
<br>email: ggrothendieck at gmail.com
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