How to load only specific functions from a package

Question

I have a package that uses the trim() function in the gdata package. I literally use nothing else from the package and (as some of you may have seen) it overwrites some functionality of base R that I need.

Is there a way to load only one function rather than the whole package?

Doesn't that assume the `gdata` is loaded in order to be able to do that? — Gavin Simpson, Oct 30 '12 at 20:16
The downside of @mplourde's method is that if you ever post your package to CRAN, folks who download it won't get `gdata` automatically downloaded for them if they don't already have it. — Josh O'Brien, Oct 30 '12 at 20:21

score 15 · Accepted Answer · edited Sep 05 '17 at 00:13

15

Sure. Just use an importFrom directive in your NAMESPACE file (as described here in R-exts).

importFrom(gdata, trim)

OP EDIT: As of R 3.2.0 there's now a base function: trimws()

edited Sep 05 '17 at 00:13

Brandon Bertelsen

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answered Oct 30 '12 at 20:14

Josh O'Brien

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score -1 · Answer 2 · answered Mar 13 '14 at 18:04

Now I get it: from another post: It means the package (In this case R) can access the package functions/objects, but the user can not without explicitly loading the tools package where as stats, graphics, etc. are loaded and ready to go for the user.

So -- the formally specified import (in which you specify 'Imports: survival' in the description file and also 'importFrom(survival, Surv)' in the NAMESPACE file does indeed work, but then, without also adding 'Surv' to the list of 'export' -ed objects, the function 'Surv' is only available to the code inside the package but not to the user (and hence not available to examples in vignettes either).

so in the NAMESPACE file add Surv to your list of exports: export("Surv", ...) — izmirlig, Jan 15 '21 at 15:08

How to load only specific functions from a package

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