I am getting into the programming language R, and I would like to know the difference between dplyr::group_by() or just group_by()?, what does this operator "::" do?.

Thanks!

CodePudding user response：

The first would be appropriate when you were uncertain that the dplyr package were loaded. The two would be equivalent if it were loaded.

CodePudding user response：

In dplyr::group_by(...), the :: operator says to load the dplyr package if necessary, and to select the group_by function from that package.

Without the dplyr:: prefix, it just says to find a function named group_by in the current environment or its ancestor environments.

Using :: is a bit safer (in a long script or package you might have created a local function named group_by and you didn't mean to run that one), but also a bit slower.

Once you're writing R packages (which is easier than you think), you can import group_by explicitly from dplyr, and get both advantages: safety and speed. It's kind of equivalent to doing

group_by <- dplyr::group_by
... many uses of group_by here ...

where you only pay the cost of :: once.