R Basics 1

Intro to Data Analytics

Jordan Ayala

Topics

Corresponds to IDS 2.1-2.3

1. Creating new files (R script and Quarto)

2. R as a calculator

3. Code chunks

4. Objects

5. Functions

   • sum()

   • c() Combine values into a vector or list

   • sort()

   • seq() Create sequence

First, open up your CMSC 121 R project folder…

Creating new folders and files

In your course RStudio project:

1. Create a new folder for in-class activities and notes: /class_activities

2. Create a new R script file Rbasics_1_activity.R

3. Create a Quarto Document file Rbasics_1_activity.qmd

R as a calculator

Try typing the following in your R script file, one line at a time:

3+4

3*12

2/5

3^2

log(4)

sqrt(34)

Prepare to run the code by either placing your cursor on the line where you have entered your code OR by highlighting the code. To run the code:

• OPTION 1: click Run on the toolbar just above your code in the Editor pane.

• OPTION 2: use the key command:

  • Mac: Command + Enter

  • Windows: Control + Enter

Code chunks

In your Quarto document, create a new code chunk and run a few basic calculations (addition, subtraction, multiplication, division, etc.)

There are a few ways to create code chunks in RStudio:

1. Place your cursor on a new line in the Quarto and type in the required characters.
2. Use the “new code chunk” button in the top right of your editor pane.
3. Use key commands:
   • Mac: Command + option + i
   • Windows: Control + option + i

Objects

In the Console type and hit Enter to run:

x <- 3

y <- 4

x <- x + 1

More objects

In your R script file type and run:

apples <- 5

pears <- 9

x <- apples + pears

Even more objects, and commenting

1. Create a new code chunk in your Quarto file.
2. Enter This is a code chunk to practice creating objects as a comment in the first line of the code chunk. Make a comment using the # symbol.

x <- 5 + 4

y <- sqrt(72)

z <- apples + pears

Answer <- x + y * z

Finally, enter the function ls() at the end of your code chunk to print out all objects you have created. You can also find these in the Environment pane.

Functions

• Functions in R are like imperative sentences (e.g. “go”,“stay”, or “sleep”).

• Telling R to use a function is described as “calling” a function.

• Call a function by typing it’s name followed by two parentheses log().

• You can create your own functions (later in the semester).

Functions and arguments

Create a new code chunk in your Quarto.

1. Add a comment in the top line.

2. Type in the sum() function. Run the code chunk.

3. Use the sum() function to add up two numbers, by adding two arguments inside the function: sum(12, 3)

Arguments specify the “what” or the “how” to a function.

4. Add another argument to the sum function using the objects you have already created.

More functions and vectors

Create a new code chunk in your Quarto.

1. Add a comment in the top line Prepare a vector to use with the sequence function.

2. Use the c() function to create a vector of the forecast high temperatures for the next 10 days in Red Hook, NY:

c(79, 78, 72, 69, 74, 79, 80, 80, 78, 76)

3. Assign the vector to an object called temps using <-
4. Use the sort function to order the vector from lowest to highest:

sort(temps)

Even more functions and arguments

Create a new code chunk in your Quarto.

1. Add a comment in the top line Calling the sequence function.

2. Use the seq() function to create a sequence of all numbers between 1 to 20.

seq(1, 20)

3. Use the seq() function to create a sequence of all even numbers between 1 to 50.

seq(1, 50, by = 2)

4. Call the sequence function to create a few more on your own.