Hmm. Good question. Not sure where I learned this. I use data.table allot for many years now.
Search https://cran.r-project.org/web/packages/data.table/vignettes/datatable-intro.html for “do in j” Read https://rawgit.com/wiki/Rdatatable/data.table/vignettes/datatable-faq.html#im-using-c-in-j-and-getting-strange-results. Then search the same document for ‘ j ‘ and selectively read what seems pertinent. That should get you most of the way there. [email protected] From: Farrel Buchinsky [mailto:[email protected]] Sent: Friday, October 20, 2017 3:31 PM To: Cook, Malcolm <[email protected]>; [email protected] Subject: Re: [datatable-help] Generating data.tables from a j function Thank you. That did it. I would still like to read more. What does one call this? What are the correct buzzwords to search for. Do you know of any blog posts / articles? On Fri, Oct 20, 2017 at 2:28 PM Cook, Malcolm <[email protected]<mailto:[email protected]>> wrote: Result.dt<-dt[ , list(sd.dtable=dtable(.SD)), by=trichotomous.variable] # untested will return a Result.dt with 2 columns: trichotomous.variable and sd.dtable The value of Result.dt[1,sd.dtable][[1]] will give the 1st groups dtable results [email protected]<mailto:[email protected]> From: [email protected]<mailto:[email protected]> [mailto:[email protected]<mailto:[email protected]>] On Behalf Of Farrel Buchinsky Sent: Friday, October 20, 2017 1:14 PM To: [email protected]<mailto:[email protected]> Subject: [datatable-help] Generating data.tables from a j function I am relatively certain that data.table can handle a function in the J position that generates a data.frame or a data.table. However, how does one handle the output? Can you please point me to a url that discusses the capability? For instance, I sometimes use the package dtables to generate descriptive statistics. It generates a table for So one could go library(dtables) dtable(dt) But what if one wanted to get descriptive statistics by a trichotomous variable dt[ , dtable(.SD), by=trichotomous.variable] I am looking for a general article or blogpost about how to handle outputs that are not single numbers or two numbers. There are functions that yield data.tables or lists or specialized objects such a models. Any suggestions? I know one can simply print the output to the console dt[ , print(dtable(.SD)_, by=trichotomous.variable] But that does not let me do anything intelligent afterwards. -- Farrel Buchinsky (412) 567-7870<tel:(412)%20567-7870> (gets me everywhere) -- Farrel Buchinsky (412) 567-7870 (gets me everywhere)
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