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I am attempting to use data.table inside a function in a package. 

combine_tot <- function(x){
    nms <- colnames(x)
    colnames(x) <- c('person', 'texts')
    x <- data.table::data.table(x)

    exp <- parse(text='list(text = paste(texts, collapse = " "))')[[1]]
    out <- x[, eval(exp),
        by = list(person, 'new' = data.table::rleid(person))][,
        'new' := NULL][]
    data.table::setnames(out, nms)
    out
}

Here is a dummy package demonstrating this: https://github.com/trinker/testdt

If I'm interactive the function works fine. If I use it in a package then I get the following error:

Error in paste(texts, collapse = " ") : object 'texts' not found

But if I run it interactively I get the following as expected:

library(data.table)
x <- data.frame(a= c('a', 'a', 's', 'f', 'd', 'a', 's', 's'), b = state.name[1:8])
combine_tot(x)

   a                    b
1: a       Alabama Alaska
2: s              Arizona
3: f             Arkansas
4: d           California
5: a             Colorado
6: s Connecticut Delaware

I've have used data.table in other similar circumstances using eval(parse but I can not make this work. What am I doing wrong?

Tyler Rinker
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  • At a guess, have you tried using `out <- x[, eval(exp, envir = environment()),`? It seems like there's an issue with scoping. – paleo13 May 12 '17 at 00:58
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    When you "run interactively", you are loading data.table and so have access to `[.data.table`, but when you run it in your own package, you are not loading/importing data.table, so instead you get `[.data.frame`... at least that seems plausible to me, as someone who hasn't made any packages. – Frank May 12 '17 at 02:12
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    Try adding `require(data.table)` in the first line of your function. – Yannis Vassiliadis May 12 '17 at 02:26
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    Inside the functions in a package, it is better not to use `library(data.table)` or `require(data.table)` – akrun May 12 '17 at 04:02
  • Should we close this as a typo / not reading the FAQ https://rawgit.com/wiki/Rdatatable/data.table/vignettes/datatable-faq.html#i-have-created-a-package-that-depends-on-data.table.-how-do-i-ensure-my-package-is-data.table-aware-so-that-inheritance-from-data.frame-works ? "Either i) include data.table in the Depends: field of your DESCRIPTION file, or ii) include data.table in the Imports: field of your DESCRIPTION file AND import(data.table) in your NAMESPACE file." You have it in Imports but have not added it to the NAMESPACE... – Frank May 12 '17 at 16:35
  • @Frank You nailed it. no on close as that's the answer. This is in no way a typo. Typo is a misspelling. There is no `not reading the FAQ` for a reason to vote to close. Both of these suggestions are inappropriate. I think the appropriate move forward is to move your comment into an answer. – Tyler Rinker May 12 '17 at 17:08
  • Ok, will do re answering. I tend to broaden that close reason to "this was misapprehension or misapplication of the documented usage", but I'm fine with leaving it open too. Just looked like you'd abandoned it. – Frank May 12 '17 at 19:04
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    Definitely a dupe – Tyler Rinker May 12 '17 at 19:41

1 Answers1

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This may be due to the fact that we are not specifying it in the 'Depends' in 'DESCRIPTION'

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The package was built, installed and was able to run the example

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NOTE: Author:, Maintainer: fields are not empty in the 'DESCRIPTION' file

NOTE2: Used the same function combine_tot with no additional changes

akrun
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