Lecture 3 STSCI 2120

How can you fill a matrix row by row in R?

• Use the argument byrow = FALSE

• Use the argument byrow = TRUE

• Use the argument byrow = NULL

• Use the argument byrow = 0

What does the matrix function in R do by default?

• Fills the matrix by row

• Fills the matrix by column

• Leaves the matrix empty

• Fills the matrix with zeros

In the POSIXct framework, what is each time represented by?

• Number of minutes since 2000

• Number of hours since 1980

• Number of seconds since 1970

• Number of days since 1990

What do double-bracketed indexes in R lists indicate?

• The subelement of an element

• The type of the list

• Which element of the list is being displayed

• The length of the list

How can you think of a data frame in R?

• As a list

• As a text document

• As R’s equivalent to the Excel spreadsheet

• As a video file

What function in R is used to create a data frame?

• data.frame

• create.frame

• frame.data

• make.frame

What are atomic vectors in R, and how can you check if an object is an atomic vector?

• A simple list of numbers; use is.list().

• A simple vector of data; use is.vector().

• A data frame object; use is.data.frame().

• A matrix of numbers; use is.matrix().

Explain the difference between a numeric (double) and an integer in R. Why might you choose to use one over the other?

• • Doubles are less precise than integers; use integers when precision is critical.

• Doubles are more flexible and can store decimal numbers, while integers are whole numbers. Use doubles when you need decimal precision.

• Integers are used when you need complex numbers, while doubles are for real numbers.

• Doubles are faster to compute with than integers in most cases.

How would you create a 3x3 matrix in R using the matrix() function, and how can you specify that the matrix should be filled row-wise instead of column-wise?

• matrix(c(1:9), ncol = 3, byrow = FALSE)

• matrix(c(1:9), nrow = 3)

• matrix(c(1:9), ncol = 3, fillrow = TRUE)

• matrix(c(1:9), nrow = 3, byrow = TRUE)

How can you load and save a CSV file in R? Provide the commands for both operations.

• load.csv() and write.csv()

• read.csv() and save.csv()

• read.csv() and write.csv()

• import.csv() and export.csv()