在 Linux 上构建的 R 包 - 对描述和命名空间中的 data.table 的特殊考虑

Question

If I use source code then everything is working but when I create package/function then it is giving me an error. Am I missing anything?

test package

test <- function() {

library("data.table")
dd <- mtcars
setDT(dd)
dd$cnt <- 1
eval(parse(text=paste0("dd <- unique(dd[,list(cnt, mpg, cyl)])")))
eval(parse(text=paste0("dd1 <- dd[order(mpg, cyl)]")))
print(dd1)

}

create a package using R CMD build on Linux

test 
   |__R
      |__test.r
   |__DESCRIPTION
   |__NAMESPACE

R CMD build test

R CMD INSTALL test_1.0.tar.gz

Content of DESCRIPTION

Package: test
Title: test
Version: 1.0
Authors@R: person("xyz", "xyz", email = "xyz@xyz.com",
                  role = c("aut", "cre"))
Description: test
Depends: R (>= 3.6.0)
License: test
Encoding: UTF-8
LazyData: true
Imports:
    data.table

use function in R

library("test")

test()

Get an error as below

Error in [.data.frame (x, i, j) : object 'cnt' not fo

R code without package and it is working

library("data.table")
dd <- mtcars
setDT(dd)
dd$cnt <- 1
eval(parse(text=paste0("dd <- unique(dd[,list(cnt, mpg, cyl)])")))
eval(parse(text=paste0("dd1 <- dd[order(mpg, cyl)]")))
print(dd1)

Answer 1

Thanks @Dirk Eddelbuettel. You are right and it worked. I found out that question have been answered on StackOverflow and also good documentation available.

https://cran.r-project.org/web/packages/data.table/vignettes/datatable-importing.html

Using data.table package inside my own package