Introduction Welcome to R for Medicine and Biology. In a nutshell, this book is: · An introduction to the R software package · A guide to managing, analyzing, and visualizing your biomedical data · An instruction manual for building a free, open-source, expandable data man- agement and analysis platform What Is R? Because you are already reading this book, you are no doubt aware that R is some kind of statistical analysis software package. That is correct. Search for this question on the Web, though, and you will find different answers. You will find that R is also described as a programming language. However, many experts talk of R in terms of being a com- plete environment--an environment that allows: · Simple and complex data analysis · Data visualization · Data management · Simple or complex programming · Connection to other software, as well as being a programming language in its own right You should think of R as an interactive computing environment. It has become popu- lar for many different reasons: · It is multiplatform, running on Windows ® and Linux ® varieties, as well as other operating systems. · R is totally free, available for download under the GNU General Public License. · R is open-source and constantly being developed by a core team. · There are a number of updates each year. · It contains more data analysis methods than any other software package. · It can be expanded by you, the user, using packages or your own programming. · R is also a community and is continuously being expanded for you by a dedi- cated group of users worldwide. Expanding the functionality of R by users is the key to its success. Expanding R is easy, as the system is modular. To start using R, you just need the base system, but xv