The post is about R Packages in the form of Questions and Answers.
Question: What version of R do I run on my computer or laptop?
Answer: To get the information about the version of R, use the following command at the R prompt.
> # get a version of R > R.version.string
You will get a result like
 “R version 3.2.1 (2015-06-18)”
Note that a package in R language is a collection of objects that R Language can use. A package contains functions, data sets, and documentation (which helps how to use the package) or other objects such as dynamically loaded libraries of already compiled code.
Question: How to check what packages are already installed?
Answer: To get a list of installed packages, write “library()” without quotation marks at the prompt. You will see the list of all of the packages installed in the local R directory of your computer system and then it will list all packages installed globally on your computer system.
> # list all packages installed > library()
You would get results like (note that results below are given as an example only, it’s not a complete list)
Packages in library ‘C:/Program Files/R/R-3.2.1/library’:
KernSmooth Functions for kernel smoothing for Wand & Jones (1995)
MASS Support Functions and Datasets for Venables and Ripley’s MASS
Matrix Sparse and Dense Matrix Classes and Methods
methods Formal Methods and Classes
mgcv Mixed GAM Computation Vehicle with Automatic Smoothness Estimation
Following is a very short list of packages installed in the local library.
abind Combine Multidimensional Arrays
AlgDesign Algorithmic Experimental Design
askpass Safe Password Entry for R, Git, and SSH
assertthat Easy Pre and Post Assertions
tibble Simple Data Frames
plyr Tools for Splitting, Applying and Combining Data
For further details on packages in R, see the link Packages in R Language.