Data Structures

Arrays

1. Explain how an array generalizes a vector.
2. Construct a given 2D array using the array function.
3. Explain (roughly) how a computer stores data structures in memory.
4. Compare and contrast column-major and row-major order for storing 2D arrays.
5. State which of column-major or row-major order R uses by default.
6. Use the [ ] operator to access a single element of a 2D array both (a) using a pair of integer indices and (b) using a single integer index.
7. Use the [ ] operator to access rows or columns of a 2D array.

Matrices

1. Construct a given matrix using the matrix function.

Lists

1. Explain how a list generalizes a vector.
2. Compare and constrast how the [ ] and [[ ]] operators access a list.
3. Access the elements of a list using both [ ] and [[ ]].
4. Use the function c to extend a vector or list.
5. Use the length function to query the length of a vector or list.
6. Use the length function to shorten a vector or list.
7. Use the names function to name the elements of a list.
8. Access the elements of a named list using both [ ] and [[ ]].
9. Access the elements of a named list using the $ operator.
10. Generate a named list using the list function.

Data Frames

1. Explain how a data frame generalizes a matrix.
2. Construct a data frame using the data.frame function.

Accessing Vectors, Arrays, Lists, and Data Frames

1. Access a collection of elements in a vector, array, list, or data frame using positive integers.
2. Access all-but a collection of elements in a vector, array, list, or data frame using negative integers.
3. Explain what the : operator does in a command such as 1:10.
4. Access entire rows or columns of a matrix or data frame using the [i, ] or [, j] syntax for the [ ] operator.
5. Explain how a vector of Booleans can be used to access the elements of a vector.