test if data.table installed.

[jimrothstein]

Not very important ....

Now:

install.packages("data.table")

Suggest:

if (!require("data.table", quietly=T)) install.packages("data.table")

[LucyNjoki]

Do I understand correctly that the package will be installed, but the startup message will be turned off?

[jimrothstein]

From https://stat.ethz.ch/R-manual/R-devel/library/base/html/library.html:

require returns (invisibly) a logical indicating whether the required package is available.

So I use require as test if installed, true or false, with no warning message.

To turn off messages during actual install.packages, I use quiet=T
https://stat.ethz.ch/R-manual/R-devel/library/utils/html/install.packages.html

fyi - I know lots and lots of ways to lookup R, but I find going directly to ref manual often gives me idea. (not the way to LEARN, only to get the story straight)
https://stat.ethz.ch/R-manual/R-devel/library/ (then choose base:: or whatever package)