Review - Cipher

Stat 251

2025-02-04

Topics to Know

Review: General Programming

Know how to:

• Define a variable
• Write a function
• Write an if/else statement
• load a package or import a library
• Create a data table structure
• Get a column, row, or value from a data table
• Get an item from a list

Vectors in R

x <- c(11, 25, 18, 4, 1, 5, 17, 22, 3,  9)

str(x)

 num [1:10] 11 25 18 4 1 5 17 22 3 9

length(x)

[1] 10

Quick-Info: how many values are below 10?

sum(x < 10)

[1] 5

which(x < 10)

[1]  4  5  6  9 10

Update values: turn all values of 3 into a 4:

Your Turn

make all square values in x negative:

1. Write a function is_square that takes a numeric vector x and returns a vector of TRUE/FALSE for each element in x (TRUE: element is square, FALSE: element is not a square number)

2. update square values by their negative number

x

 [1] 11 25 18  4  1  5 17 22  4  9

is_square(x):

 [1] FALSE  TRUE FALSE  TRUE  TRUE FALSE FALSE FALSE  TRUE  TRUE

updated x:

 [1]  11 -25  18  -4  -1   5  17  22  -4  -9

Homework - Review

• in Canvas, accept the Github Classroom link to homework #3

• Clone the repository to your local machine

• Render the file index.qmd

Homework - Cipher

• Not all statements that execute are correct (Part 1: fix mistakes)

• Part 2: write a decoder

• Part 3: Decode the secret message!

Next Time

• Continue working on Homework 3

• Self Assessment quiz due Thursday