<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN">
<html><body>
<p> </p>
<p>But data.table is floating point aware. You _can_ join to floating point values, and you _can_ group by floating point values. data.table will do that within machine tolerance and take care of it for you.</p>
<p>So this may explain why your 'agg' only had 119 rows (because data.table is doing the rounding for you automatically), but length(unique(DT$x)) had 331 ?</p>
<p>But, there was a bug or two in this area a few versions ago, mentioned in NEWS. Which is why I asked for sessionInfo() and str(DT) suspecting you had a double column with a slightly older version of data.table. Or, there might be a new problem. If you have to round() in data.table, that doesn't sound right to me.</p>
<p>Matthew</p>
<p> </p>
<p>On 10.04.2013 13:50, David Bellot wrote:</p>
<blockquote type="cite" style="padding-left:5px; border-left:#1010ff 2px solid; margin-left:5px; width:100%"><!-- html ignored --><!-- head ignored --><!-- meta ignored -->
<div dir="ltr">
<div class="gmail_default" style="font-family: arial,helvetica,sans-serif; font-size: small;">actually I found the issue. That was not related to data.table but because I'm comparing float values, it breaks all the time if I do not round() my values before. Basically I have values like 0,1, 1.5, 0.5 etc...</div>
<div class="gmail_default" style="font-family: arial,helvetica,sans-serif; font-size: small;">I know it's bad to do that but I'm not the boss in this project ;-)<br /><br /></div>
<div class="gmail_default" style="font-family: arial,helvetica,sans-serif; font-size: small;">Just in case other users are reading my email, I can only advise to read that again and again:<br /><a href="http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html">http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html</a><br /><br /></div>
<div class="gmail_default" style="font-family: arial,helvetica,sans-serif; font-size: small;"><span style="color: #003366;"><span style="font-family: Verdana, Arial, Helvetica, sans-serif;">Best,<br />David</span></span></div>
<div class="gmail_extra"><br /><br />
<div class="gmail_quote">On Tue, Apr 9, 2013 at 11:39 AM, Matthew Dowle <span><<a href="mailto:mdowle@mdowle.plus.com">mdowle@mdowle.plus.com</a>></span> wrote:<br />
<blockquote class="gmail_quote" style="margin: 0 0 0 .8ex; border-left: 1px #ccc solid; padding-left: 1ex;"><span style="text-decoration: underline;"></span>
<div>
<p> </p>
<p>That's odd. Please provide result of sessionInfo() and str(DT).</p>
<p>Matthew</p>
<div>
<div>
<p> </p>
<p>On 09.04.2013 11:32, David Bellot wrote:</p>
<blockquote style="padding-left: 5px; border-left: #1010ff 2px solid; margin-left: 5px; width: 100%;">
<div dir="ltr">
<div class="gmail_default" style="font-family: arial,helvetica,sans-serif; font-size: small;">Hi,<br /><br /></div>
<div class="gmail_default" style="font-family: arial,helvetica,sans-serif; font-size: small;">I have a data.table DT with one of the column named x and I other names, let's say, a1, a2, ... aN. The key of this data.table is made of a1...aN.<br /><br /></div>
<div class="gmail_default" style="font-family: arial,helvetica,sans-serif; font-size: small;">Later on, I aggregate my DT with x like this:<br />agg = DT[ , list(m=mean(y), c=length(y)), by = c("x") ]<br /><br /></div>
<div class="gmail_default" style="font-family: arial,helvetica,sans-serif; font-size: small;">The problem is that "x" has 331 unique values as found by length(unique(DT$x)) but my result "agg" only has 119 rows. I tried by changing the key to "x" alone but the problem persists. My DT table has a few millions rows by the way.</div>
<div class="gmail_default" style="font-family: arial,helvetica,sans-serif; font-size: small;"><br />I'm sure I'm missing something totally obvious :-( !!!!<br /><br /></div>
<div class="gmail_default" style="font-family: arial,helvetica,sans-serif; font-size: small;">Any idea ?</div>
<div class="gmail_default" style="font-family: arial,helvetica,sans-serif; font-size: small;">Best,<br />David</div>
</div>
</blockquote>
<p> </p>
<div> </div>
</div>
</div>
</div>
</blockquote>
</div>
</div>
</div>
</blockquote>
<p> </p>
<div> </div>
</body></html>