<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><p>Michael,</p>
<p>Note that in your case, you can also do:</p>
<pre><code>DT <- data.table(a = 1:4, b = 8:5)
for (i in c("a", "b"))
DT[order(DT[[i]])]
</code></pre>
<p>At the moment, I’m more inclined towards giving an error when any of the arguments to <code>order(.)</code> results in a <code>list</code>. The message could be something like:</p>
<pre><code>DT[order(.)] on data.tables is optimised internally to use data.table's fast ordering. Since the behaviour of base:::order seems inconsistent in the way it handles list input - for ex: compare DT[order(list(x))] and DT[order(data.table(x))], we do not support list columns as input here. If you're sure, you can use `DT[base:::order(.)]` explicitly. However, this can be avoided most of the times by using `[[` to access specified columns to result in a vector.
</code></pre>
<p>What do you (all) think?</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_sign_1403309724158471168" 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">Arunkumar Srinivasan</span> <a href="mailto:aragorn168b@gmail.com">aragorn168b@gmail.com</a><br>Reply: <span style="color:black">Arunkumar Srinivasan</span> <a href="mailto:aragorn168b@gmail.com">aragorn168b@gmail.com</a><br>Date: <span style="color:black">June 20, 2014 at 11:47:22 PM</span><br>To: <span style="color:black">Michael Smith</span> <a href="mailto:my.r.help@gmail.com">my.r.help@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 style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div></div><div>
<title></title>
<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>
<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">
<div>
<div><span>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>
>> _______________________________________________<br>
>> datatable-help mailing list<br>
>> datatable-help@lists.r-forge.r-project.org<br>
>>
https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help<br>
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</blockquote>
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