• answer depends on who you ask and what they use R for

• environment for statistical computing, graphics and programming

• originally created by Ross Ihaka and Robert Gentleman (1996)

• currently maintained by international R-core development team

• many, many people also contribute to R and the wider
  R community

• it allows you to keep an exact and reproducible
  record of your analyses

• transparent

• other people* can reproduce your analysis

• easily share your code (GitHub)

• open science

• excellent graphics capabilities

• employability

• opportunity to get involved
  with a fantastic and supportive
  community

• commands are typed in the editor and then sourced into the console
  at the > prompt

> 2 + 2
## [1] 4

• R is object orientated. You can create variable and assign value(s) to them

> a <- 2 + 2
> a
## [1] 4

• once created, operations can be performed on variables

> a <- 2 + 2
> b <- 3 * 2
> 
> a + b
## [1] 10

• this is very powerful and flexible

• much of the functionality of R is enhanced by using variables called functions

• functions contain a set of instructions that allow you to perform a specific task(s)

• you can use functions that are inbuilt in R

> numbers <- c(2, 3, 4, 5, 6)   # use the concatenate function
> numbers
## [1] 2 3 4 5 6
> 
> mean(numbers)                 # use mean function
## [1] 4
> 
> var(numbers)                  # use variance function
## [1] 2.5

• comments (#) are ignored by R

• or you can install user contributed packages to increase versatility and power

• there are packages for almost anything

• install packages from CRAN, Bioconductor and GitHub

• packages are easy to install in R

• or write your own functions

• function to calculate standard error

> numbers <- c(2, 3, 4, 5, 6)    # use the concatenate function
> 
> se.fnc <- function(x){         # start function for se
+  std.x <- sd(x)                     # calculate SD
+  nos.x <- length(x)                 # calculate number obs
+  se.x <- std.x/(sqrt(nos.x))   # calculate SE
+  print(se.x)    
+ }
> 
> se.fnc(numbers)                # use your new function
## [1] 0.7071068

• R is case sensitive A is not the same as a

• commands are generally separated by a new line, but you can also use a ; (rare)

• anything that follows the hash symbol (#) will be ignored by R. Use this to comment your code

• a series of commands can be grouped using braces { }

• write pretty code by following a code style guide

• by default plots are displayed in the 'Plots' pane in RStudio

• plots can be copied and pasted into your word processor of choice

• better to export plots to an external file (jpeg, pdf, png etc)

• R has extensive help facilities

• from within R the main method of getting help is to use the help() function

> help("plot")    # open help file for the function plot

or equivalently

> ?plot

• or to search the help files use help.search("plot") or ??plot

• Google it!: Try Googling any error messages you get. It's not cheating and everyone does it! You'll be surprised how many other people have probably had the same problem and solved it.

• Stack Overflow: There are many thousands of questions relevant to R on Stack Overflow

• Here are the most popular ones, ranked by vote. Make sure you search for similar questions before asking your own

• make sure you include a reproducible example to get the most useful advice. A reproducible example is a minimal example that lets others who are trying to help you to see the error themselves.

• use R often and use it regularly

• learning R is not a memory test, you have your R scripts

• you don’t need to know everything there is to know about R to use it productively

• staring at code for hours is not good for you. Walk away for a few minutes

• there are many ways to tackle a particular problem. See what others have done

• recognise that there will be times when things will get a little tough or frustrating. Try to accept these periods as part of the natural process of learning a new skill (we’ve all been there) and remember, the time and energy you invest now will be more than payed back in the not too distant future.