<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><p>This is a really tricky one. I was just trying to fix it when I recollected the issues with <code>base:::order</code> from the time during implementation.</p>
<p>Consider this case:</p>
<pre><code>require(data.table)
DT <- data.table(x=c(1,4,3,2), y=c(8,6,5,7), z=c(10,12,11,9))
</code></pre>
<p>Consider the cases A and B below:</p>
<pre><code># case A
DT[base:::order(DT[, "x", with=FALSE])]
# x y z
# 1: 1 8 10
# 2: 2 7 9
# 3: 3 5 11
# 4: 4 6 12
</code></pre>
<p>Intended right result. Great!</p>
<h3 id="b:">B:</h3>
<pre><code># case B
DT[base:::order(list(x))]
# x y z
# 1: 1 8 10
</code></pre>
<p>What just happened?!? So, basically if the list gives <code>TRUE</code> for <code>is.object(.)</code>, it understands what the opeation is, correctly. But if it’s <em>just</em> a list, no idea how to deal with it. Also it silently returns undesirable result (imo).</p>
<p>Similar to the above cases, compare these two:</p>
<pre><code># case C
DT[base:::order(DT[, "x", with=FALSE], DT[, "y", with=FALSE])]
# vs
# case D
DT[base:::order(list(x), list(y))]
</code></pre>
<h3 id="evenmorecrazycase:">Even more crazy case:</h3>
<pre><code># case E
DT[base:::order(DT[, c("x", "y"), with=FALSE])]
# vs
# case F
DT[base:::order(list(x,y))]
</code></pre>
<p>While we were testing and implementing <code>forder</code>, obviously it dint occur to check with the argument to <code>order(.)</code> with a <code>data.table</code>. And in spite of the fact that the output for <code>DT[order(list(x))]</code> is a bit strange and even dangerous, to be consistent with <code>base:::order</code>, we had implemented it the same way.</p>
<p>Now, I’m not so sure.. Any ideas justifying these differences?</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;"><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;"><br></div> <div id="bloop_sign_1403300011687880960" 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">Michael Smith</span> <a href="mailto:my.r.help@gmail.com">my.r.help@gmail.com</a><br>Reply: <span style="color:black">Michael Smith</span> <a href="mailto:my.r.help@gmail.com">my.r.help@gmail.com</a><br>Date: <span style="color:black">June 15, 2014 at 5:02:46 AM</span><br>To: <span style="color:black">G See</span> <a href="mailto:gsee000@gmail.com">gsee000@gmail.com</a><br>Cc: <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"> Re: [datatable-help] `with=F` in the `i` Argument <br></span></div><br> <blockquote type="cite" class="clean_bq"><span><div><div></div><div>Devs,
<br>
<br>Is this a bug? It works in 1.9.2 but not in the 1.9.3 development version:
<br>
<br>DT <- data.table(a = 1:4, b = 8:5)
<br>for (i in c("a", "b"))
<br> print(DT[order(DT[, i, with = FALSE])])
<br>
<br>Error in forder(DT, DT[, i, with = FALSE]) :
<br> Column '1' is type 'list' which is not supported for ordering currently.
<br>
<br>
<br>Thanks,
<br>
<br>M
<br>
<br>
<br>On 05/31/2014 12:44 PM, G See wrote:
<br>> Hi Michael,
<br>>
<br>> I would use get()
<br>>
<br>> DT <- data.table(a = 1:4, b = 8:5)
<br>> for (i in c("a", "b"))
<br>> print(DT[order(get(i))])
<br>>
<br>> For what it's worth, your solution doesn't seem to work in data.table
<br>> 1.9.3 (svn rev. 1278):
<br>>
<br>>> for (i in c("a", "b"))
<br>> + print(DT[order(DT[, i, with = FALSE])])
<br>> Error in forder(DT, DT[, i, with = FALSE]) :
<br>> Column '1' is type 'list' which is not supported for ordering currently.
<br>>
<br>>
<br>> HTH,
<br>> Garrett
<br>>
<br>> On Fri, May 30, 2014 at 11:01 PM, Michael Smith <my.r.help@gmail.com> wrote:
<br>>> All,
<br>>>
<br>>> I'm trying to order the rows according to several columns at a time:
<br>>>
<br>>> DT <- data.table(a = 1:4, b = 8:5)
<br>>> for (i in c("a", "b"))
<br>>> print(DT[order(i), with = FALSE])
<br>>>
<br>>> It doesn't work, since `with` seems to be about the `j` argument, but
<br>>> not the `i` argument, according to `?data.table`.
<br>>>
<br>>> I found the following workaround, but wonder whether there is a more
<br>>> elegant way to do it:
<br>>>
<br>>> for (i in c("a", "b"))
<br>>> print(DT[order(DT[, i, with = FALSE])])
<br>>>
<br>>> Thanks,
<br>>> M
<br>>> _______________________________________________
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