To see what packages are already installed on your system, use the following command;
This command will return a matrix with a row for each package installed on your system. The output matrix contains detailed information about each package. The two most important columns of this output are package and priority.
The package column gives the name of the package and priority column indicates that what is needed to use function from the package.
- If priority is “base” then the package is already installed with base R. All of its functions are available upon opening R.
- If priority is “recommended” then the package was installed with base R, but not loaded. Before using the command from this package, the user will have to load it with the library function. For example, library(MASS).
- If priority is “NA”, then the package was installed by the user (that is, did not come with base R), but not loaded. Before using the commands from this package, the user will have to load it with the library command.