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<div class="moz-cite-prefix"><br>
Agreed, intentional.<br>
<br>
> L = list(1,2,3)<br>
> as.data.table(L)<br>
V1 V2 V3 # 3 columns, not one list column<br>
1: 1 2 3<br>
<br>
> L = list(1,2,3,list("a",4L,3:10)) # the one nested list
here creates one list column<br>
> as.data.table(L)<br>
V1 V2 V3 V4<br>
1: 1 2 3 a<br>
2: 1 2 3 4<br>
3: 1 2 3 3,4,5,6,7,8,<br>
<br>
Rick - are you asking for use cases of list columns full stop or
use cases of converting nested lists to data.table containing list
columns ?<br>
<br>
<br>
On 08/08/13 04:30, Ricardo Saporta wrote:<br>
</div>
<blockquote
cite="mid:CAE7Aa4SdmysbcACWouea-eoYHYEhc=q-+KTyFMKoLvHLzp_AHw@mail.gmail.com"
type="cite">
<div dir="ltr">Hey Frank,
<div><br>
</div>
<div>Thanks for pointing out that SO link, I had missed it. </div>
<div><br>
</div>
<div>All, </div>
<div><br>
</div>
<div>I'm curious as to which used cases this functionality would
be used in (used for?)</div>
<div><br>
</div>
<div>thanks, </div>
<div>Rick </div>
<div><br>
</div>
<div class="gmail_extra">
<br>
<br>
<div class="gmail_quote">On Wed, Aug 7, 2013 at 8:14 PM, Frank
Erickson <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:FErickson@psu.edu" target="_blank">FErickson@psu.edu</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div>Hi Rick,</div>
<div><br>
</div>
<div>I guess it's intentional: Matthew saw this SO
question (since he edited one of the answers): <a
moz-do-not-send="true"
href="http://stackoverflow.com/questions/9547518/creating-a-data-frame-where-a-column-is-a-list"
target="_blank">http://stackoverflow.com/questions/9547518/creating-a-data-frame-where-a-column-is-a-list</a></div>
<div><br>
</div>
<div>Some musings: Of course, to reproduce
as.data.frame-like behavior, you can un-nest the list,
so both functions treat it the same way.</div>
<div><br>
</div>
<blockquote style="margin:0 0 0
40px;border:none;padding:0px">
<div>Z <- unlist(Y,recursive=FALSE)</div>
<div><br>
</div>
<div>
<div>identical(as.data.table(Z),as.data.table(as.data.frame(Z)))
# TRUE</div>
</div>
<div>
<div># or, equivalently (?)</div>
</div>
<div>
<div>identical(do.call(data.table,Z),data.table(do.call(data.frame,Z)))
# TRUE</div>
</div>
</blockquote>
<div><br>
</div>
<div>On the other hand, going back the other direction
(getting data.table-like behavior when data.frame's is
the default) is more awkward, as seen in that SO
question (where they mention protecting each sublist
with the I() function). Besides, I'm with @flodel, who
asked the SO question, in expecting data.table's
behavior: one top-level item in the list mapping to one
column in the result...</div>
<div><br>
</div>
<div>--Frank</div>
<div><br>
<div class="gmail_quote">
<div>
<div class="h5">On Wed, Aug 7, 2013 at 4:56 PM,
Ricardo Saporta <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:saporta@scarletmail.rutgers.edu"
target="_blank">saporta@scarletmail.rutgers.edu</a>></span>
wrote:<br>
</div>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div>
<div class="h5">
<div dir="ltr">
<div>Hi all, <br>
</div>
<div><br>
</div>
<div>Note the following discrepancy in
structure between as.data.frame &
as.data.table when called on a nested list.</div>
<div>as.data.frame converts the sublist into
individual columns whereas as.data.table
stacks them into a single column and creates
additional rows. </div>
<div><br>
</div>
<div>Is this intentional? </div>
<div>-Rick</div>
<div><br>
</div>
<div><br>
</div>
<div>
<div>as.data.frame(X)</div>
<div># start type end
data.editDist data.second</div>
<div># 1 start_node is_similar end_node
1 HelloWorld</div>
<div><br>
</div>
<div>as.data.table(X)</div>
<div># start type end
data</div>
<div># 1: start_node is_similar end_node
1</div>
<div># 2: start_node is_similar end_node
HelloWorld</div>
</div>
<div>
<br>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div>### Copy+Paste'able Below ###</div>
<div><br>
</div>
<div># Example 1:</div>
<div>X <- structure(list(start =
"start_node", type = "is_similar", end =
"end_node", </div>
<div> data = structure(list(editDist = 1,
second = "HelloWorld"), .Names =
c("editDist", </div>
<div> "second"))), .Names = c("start",
"type", "end", "data"))</div>
<div><br>
</div>
<div>as.data.frame(X)<br>
</div>
<div>as.data.table(X)</div>
<div><br>
</div>
<div>as.data.table(as.data.frame(X))</div>
<div><br>
</div>
<div><br>
</div>
<div># Example 2, with more elements:</div>
<div>Y <- structure(list(start =
c("start_node", "start_node"), type =
c("is_similar", "is_similar"), end =
c("end_node", "end_node"), data =
structure(list(editDist = c(1, 1), second =
c("HelloWorld", "HelloWorld")), .Names =
c("editDist", "second"))), .Names =
c("start", "type", "end", "data"))</div>
<div><br>
</div>
<div>as.data.frame(Y)</div>
<div>as.data.table(Y)</div>
<div><br>
</div>
</div>
<br>
</div>
</div>
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