scope - What are the double colons (::) in R? -

i following tutorial in rbloggers , found use of double colons, looked online, couldn't find explanation use. here example of use.

df <- dplyr::data_frame(   year = c(2015, na, na, na),    trt = c("a", na, "b", na) )

i understand creates data frame don't understand purpose.

as have looked page usage of :: helps access exact function specific package. when load dplyr got message the

the following objects masked ‘package:base’:        intersect, setdiff, setequal, union

so, instance use respective intersect functions ...the usage follows

mtcars$model <- rownames(mtcars) first <- mtcars[1:20, ] second <- mtcars[10:20, ] dplyr::intersect(first, second) base::intersect(first, second)

run , check differences. here resources understanding.

Ben