Multiple Choice Questions for Subsetting in R

My MCQs are based off the Analyzing Patient Data lesson on R Programming, starting more simply with vectors and then moving to matrices.

Question 1

Given the following line of code used to generate vector 'x', how would you subset the first element?

x <- c(10, 20, 30)

• A. x(1)
• B. x[1]
• C. x[0]
• D. X[1]

Question 2

Given the following line of code to generate matrix 'y', how would you subset the second row?

y <- matrix(nrow=2, ncol=3, 1:6)

• A. y[nrow=2]
• B. y[2]
• C. y[,2]
• D. y[2,]

Misconceptions

• A. the nrow argument is used in the function for generating the matrix, not in subsetting an object
• B. this is the incorrect number of dimensions (1); there should be a comma to index both the row(s) and column(s) in the 2-dimensional matrix
• C. the second column has been subset instead of the second row
• D. correct answer