Question

How to check installed packages from r source?

Answer 1

Use installed.packages() or find.package() function and pass the name of packages to be found as a vector separately in the function.

> find.package("dplyr")
[1] "C:/Users/Cherukuri_Sindhu/Documents/R/win-library/3.6/dplyr"

If not found, then 

Error in find.package("dplyr1") : there is no package called ‘dplyr1’