Homework 1

R Basics

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Problem 1:

From set = {1.5, 15, 0, 54, 23}, pick two numbers and perform the Following Operations:

.Subtraction .Multiplication .square root

#Subtraction
15-1.5

## [1] 13.5

#Multiplication
15*1.5

## [1] 22.5

#Square Root
sqrt(15)

## [1] 3.872983

Problem 2

Suppose you have a set of numbers representing the assignments scores:

scores <- c(87,100, 91, 95, 81.5, 0, 39, 74, 92)

#Calculate the average of the scores, and round your answer to two decimal number
round(mean(scores),2)

## [1] 73.28

#Find the Maximum and Minimum score
max(scores)

## [1] 100

min(scores)

## [1] 0

#Find how many scores were above the average, use coding for this
#TRUE is equivalent to 1, so we use sum to add up all the TRUEs in scores>mean(scores), effectively counting the number of entries in scores that are above average 
sum(scores>mean(scores))

## [1] 7

#Create a new set called new_scores that includes the elements from indices 2 to 6 of the scores vector
new_scores <- scores[2:6]

Problem 3:

Read section 2.3, then answer the following questions

# Create a vector with the number 1 repeated 5 times. Print it
# Use the rep() function to repeat 1 five times
x <- rep(1, times=5)
print(x)

## [1] 1 1 1 1 1

# Create a vector with a sequence of numbers from 1 to 10 with a step of 2. Print it
# Use the seq function
my_vec1 <- seq(from=1, to=10, by=2)
print(my_vec1)

## [1] 1 3 5 7 9

# Create a vector by repeating a sequence from 1 to 3, 2 times. Print it.
# Embed the seq function in the rep function. seq() creates a sequence from 1 to 3, and rep() repeats it.
my_vec2 <- rep(seq(from=1, to=3), times= 2)
print(my_vec2)

## [1] 1 2 3 1 2 3

Problem 4

mixed_vector <- c(1, "two", 3.0, TRUE, 2)

# Check the class of the vector
class(mixed_vector)

## [1] "character"

## Coerce to numeric and print it 
# Changes the "two" to NA. Also changes "TRUE" to NA because it has already been coerced to character type. 
print(as.numeric(mixed_vector))

## Warning in print(as.numeric(mixed_vector)): NAs introduced by coercion