Programming in R

Question 1

Five basic or “atomic” classes of objects in R

Answer 1

• Character
• Numeric (Real Numbers)
• Integer
• Complex
• Logical (True/False)

Question 2

The most basic object in R

Answer 2

A Vector - can only contain objects of the same class (except lists)
- Empty vectors can be created with the “vector()” function

Question 3

Attributes of R objects?

Answer 3

• Names, dimness (dimension names)
• Dimensions (matrices, arrays)
• Class
• Length
• Other
• Accessible using the “attributes()” function

Question 4

What operator is used in R to create an integer sequence?

Answer 4

A colon eg. [1:20]

Question 5

What is “coercion” in R?

Answer 5

This is when objects in R are mixed in the same vector and so R simplifies to the least common denominator to make them of the same class

Question 6

What is a matrix in R?

Answer 6

A matrix is a veto with a dimension attribute. The dimension is itself an integer vector of length 2 (now, ncos)

Matrices are constructed “column-wise” starts at the top of a column and goes down through rwo, then start top of next column until complete.

Question 7

Whit is cbind-ing and rbinding of matrices in R?

Answer 7

Column-binding and row-binding with cbind() and rbind(); cbind() lists the objects in a vertical order, rbind() in a horizontal order

Question 8

What is a list in R?

Answer 8

Lists are a special type of vector in R that can contain elements of different classes. lists are very important in R. and used for many things. Elements in lists have double brackets around them.

Question 9

What is a “Factor” in R?

Answer 9

A Factor represents categorical data that is ordered or unordered, like an integer vector where each integer has a label (eg/ Male and Female instead of 1 and 2.