Remind students to install R and RStudio.

Have students open RStudio and check to see if console “sees” R.

R

• Programming language
• Statistics and data analysis environment

RStudio

• IDE - Integrated Development Environment
  • Interpreter/Console
  • Text editor
    • object highlighting
    • information about problems with code
    • tab key autocompletes
      • Let the computer do repetitious work.
      • It’s easier and with fewer mistakes.
  • Environment/History
  • Project management

Create new folder for scripts

Basic expressions

• Write code directly in the interpreter
• Kangaroo rat weight (g -> lb)

50
50 / 1000
50 / 1000 * 2.2

• Write code in text editor and run either by line or all code

50
50 / 1000
50 / 1000 * 2.2

• Source vs Source with Echo

Create notes R script, put in new folder

Variables

• A variable is a name that has a value associated with it
  • Assign using <- or =

weight_g <- 50
weight_g = 50

• It works just like the value itself

weight_g / 1000
weight_g / 1000 * 2.2
weight_lb <- weight_g / 1000 * 2.2

• It won’t change unless you assign a new value to it directly

weight_g
weight_g * 2
weight_g
weight_g <- 26
weight_g

Comments

• Remember what code is doing
• For humans, not computers
• Use the #

# Calculate weight of Kangaroo Rat in pounds

Assignments format

• Comment before each problem and each sub-problem
• Make sure result prints out on Source with echo

# Problem 1

# 1.1
2 + 2

# 1.2
2 - 8

# Problem 2

width = 2
height = 3
length = 1.5
volume = width * height * length
volume

Create assignment script, put in new folder

• Now we’re going to work on some exercises to get a feel for this
• In class we will often only do part of an exercise and save the rest for later
• I use an in-class feedback system to get a feel for when most folks are done and how well folks understand the material
• When you are done with the part of the exersise we are doing for class, click on the In class feedback link and fill out the poll
• Two sections
  • 1-5 rating for how well you understand what we just covered
  • A text box to describe anything confusing you if you can describe it
  • 4 and 5’s indicate that you’re following things and we can move on
  • 3’s and below suggest we need to chat more

Do Exercise 1.1-1.3 - Basic Expressions

Do Exercise 2 - Basic Variables

Functions

• A function is a complicated expression.
• Command that returns a value
• Hides the details of how that value is determined.
• Useful - don’t want to know how numbers are rounded

sqrt(weight_lb)
sqrt(0.11)

• A function call is composed of two parts.
  • Name of the function
  • Arguments that the function requires to calculate the value it returns.
  • sqrt() is the name of the function, and 0.11 is the argument.
• Another function that we’ll use a lot is print()
• It lets us explicitly print things out
• One argument - the thing you want to print

print(weight_lb)

• When we run the whole file using Source this value gets printed
• Source w/o echo
• Use this for output we want the program to produce

• Use this in your assignments to print out the answers

• Functions can take multiple arguments.
  • Round weight_lb to one decimal place
  • Typing round() shows arguments
  • Number to be rounded and number of digits

round(0.11, 1)
round(weight_lb, 1)

• Save the output of a function by assigning it to a variable

weight_rounded <- round(weight_lb, 1)
weight_rounded

Do Exercise 4.1-4.3 - Built-in Functions

• If you don’t save the output of a function then there is no way to access it

mass_kg <- 0.5163
round(mass_kg, 2)

• It is common to forget this when dealing with variables and expect the variable to have changed

mass_kg

Types

• All values have types

str(weight_lb)
str('hello world')