## 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*