1.2 — Meet R — Class Content

Preliminary Statistics Survey Due Sunday August 29

Please take the preliminary survey on your statistics and software background by 11:59 PM Sunday. This will help us all have a productive semester together.

Installing R and R Studio

We will be using Rstudio.cloud, for which you have made a free account. However, since R is free, I strongly recommend you download and install it on your own computers. You may decide also you prefer to use your own computers in class when we work with R.

1. Install R from CRAN¹ by clicking “Download R” (or the CRAN link under Downloads on the left menu). This will take you to a mirrors page, where you can select a location in the U.S. and download a copy of R
2. Install R Studio (Desktop Version), choose the “Free” option

(This will also be posted on the Reference page.)

R Packages

Packages come from multiple sources.

The polished, publicly released versions are found on CRAN. When installing a package available on CRAN, it is sufficient simply to tell R the following:²

install.packages("packagename") 

Other packages, which may be in various developmental states (including perfectly functional!) are often hosted on GitHub before they make their way onto CRAN. Simply telling R install.packages("packagename") will fail to find it (as R only looks in CRAN for packages), so you must use another package called devtools³ to install packages directly from Github:⁴

devtools::install_github("username/packagename") 

For example, to install Hadley Wickham’s package r4ds from its Github page https://github.com/hadley/r4ds, we would type:

devtools::install_github("hadley/r4ds")

To use a package, you need to ensure it is loaded to your workspace (you only need to do this once)^[When we learn how to write R Markdown documents, . with library("package_name").⁵

Other Useful Commands to Know

One of the best/worst things about R is that it is a language, meaning there are multiple ways that you can accomplish the same task. Here are a few alternative methods relevant to what we have learned so far that might prove useful.

1:5 # create a vector of 1 through 5

## [1] 1 2 3 4 5

12:17 # create a vector of 12 through 17

## [1] 12 13 14 15 16 17

seq(from = 1, to = 10, by = 2) # sequence from 1 to 10, by 2s

## [1] 1 3 5 7 9

# note you do not need to fully write out the name of each argument, just the input!

seq(32.5,40,1.5) # sequence from 32.5 to 40, by 1.5

## [1] 32.5 34.0 35.5 37.0 38.5 40.0

rep(2, times = 4) # repeat "2" four times

## [1] 2 2 2 2

rep(2, 4) # does the same thing

## [1] 2 2 2 2

# the thing repeated could itself be a vector
rep(c(1,4,7), 3) # repeat the vector "1, 4, 7" three times

## [1] 1 4 7 1 4 7 1 4 7

# combine (the sequence of 4 to 8 by 2's repeated three times) and 1 and 5

c(rep(seq(4,8,2),3),1,5)

##  [1] 4 6 8 4 6 8 4 6 8 1 5

Suggested Style Guide for Coding

We want to maximize human-readability of code, not just machine-readability. I try to follow Hadley Wickham’s style guide for all of my code, including that in this class.

You will not be graded on the style of your code. But now’s the best time to learn best practices (while you don’t know any alternatives!) to save yourself and your potential colleagues (including your future self) from unnecessary frustration.

• comment above for overall idea
• comment on side for individual elements of long commands
• name with _
• use %>% wherever possible
• spaces betweeen all operators: <-, =, +, etc.
  • Exception: : and ::
• line breaks between multiple arguments to a function

p<-ggplot(data=data, aes(x=x,y=y,fill=fill))+geom_point()

becomes

p <- ggplot(data = data,
       aes(x = x,
           y = y,
           fill = fill))+
  geom_point()