Skip to content

extend env vignette for common trap, closes #6031 #6923

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
ben-schwen merged 3 commits into from
Apr 30, 2025
Merged

extend env vignette for common trap, closes #6031 #6923

Changes from 1 commit
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
26b84b1
extend env vignette for common trap, closes #6031
jangorecki Apr 24, 2025
859a1d2
Wording correction from Ben
jangorecki Apr 30, 2025
315e3be
Another wording improvement by Ben
jangorecki Apr 30, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
13 changes: 13 additions & 0 deletions vignettes/datatable-programming.Rmd
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -376,6 +376,19 @@ print(j)
DT[, j, env = list(j = j)]
```

### Common mistakes

It is important to understand the difference between passing an object and a name that points to an object. See the verbose output of following examples.

```{r obj_vs_objname}
DT[, fun(Petal.Width), env = list(fun = mean), verbose=TRUE]
DT[, fun(Petal.Width), env = list(fun = "mean"), verbose=TRUE]
```

User will usually want to substitute function name rather than function body.

In case of any doubts on the `env` interface functioning user is advised to look at `verbose` output.

## Retired interfaces

In `[.data.table`, it is also possible to use other mechanisms for variable substitution or for passing quoted expressions. These include `get` and `mget` for inline injection of variables by providing their names as strings, and `eval` that tells `[.data.table` that the expression we passed into an argument is a quoted expression and that it should be handled differently. Those interfaces should now be considered retired and we recommend using the new `env` argument, instead.
Expand Down
Loading