Functions: Functions with Whole Vectors

Question 1

length()

Answer 1

10 students from two different classes took two exams.

function allows you to count the number of scalars in a vector

#Here are three vectors showing the data
midterm <- c(62, 68, 75, 79, 55, 62, 89, 76, 45, 67)
final <- c(78, 72, 97, 82, 60, 83, 92, 73, 50, 88)

length(midterm)
##[1] 10

Question 2

adding to whole vectors

Answer 2

Add 5 to each midterm score (extra credit!)

midterm <- midterm + 5
midterm
##[1] 67 73 80 84 60 67 94 81 50 72

we previously made two vectors, final and midterm, and we can manipulate all of the numbers in each using simple numerical operators

Question 3

subtracting whole vectors

Answer 3

Difference between final and midterm scores

final - midterm
##[1] 11 -1 17 -2 0 16 -2 -8 0 16

Question 4

arithmetic operations on vectors

Answer 4

a <- c(1, 2, 3, 4, 5)
b <- c(10, 20, 30, 40, 50)

a + 100
##[1] 101 102 103 104 105

Notice how when using a vector and an arithemtic operator, the operation occurs on all of the scalars in the vector, not just on one number

Question 5

operating on vectors with a single scalar

Answer 5

If you do an operation on a vector with a scalar, R will apply the scalar to each element in the vector

(a + b) / 10
##[1] 1.1 2.2 3.3 4.4 5.5

a ^ 2
##[1] 1 4 9 16 25 36 49 64 81 100

a <- 1:10
a / 100
##[1] 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10

Question 6

basic math with multiple vectors

Answer 6

a <- 1:5
b <- 1:5

ab.sum <- a + b
ab.diff <- a - b
ab.prod <- a * b

ab.sum
##[1] 2 4 6 8 10

notice how vectors are being made using existing vectors.