R Basics Exercise - Solutions

We will test you on a few topics:

  • Basic Data Types
  • Basic Arithmetic
  • Vector
  • Vector Operations
  • Comparison operators
  • Vector Selection and Indexing

The exercises below should be straightforward if you've reviewed the lecture, don't expect something very challenging yet, this is more of a review to make sure you've understood everything so far! Later on exercises/projects will be more challenging (and a lot more fun!)

Solve the following problems using R

What is two to the power of five?

In [1]:
2^5
Out[1]:
32

Create a vector called stock.prices with the following data points: 23,27,23,21,34

In [4]:
stock.prices <- c(23,27,23,21,34)
stock.prices
Out[4]:
  1. 23
  2. 27
  3. 23
  4. 21
  5. 34

Assign names to the price data points relating to the day of the week, starting with Mon, Tue, Wed, etc...

In [6]:
names(stock.prices) <- c('Mon','Tues','Wed','Thu','Fri')
stock.prices
Out[6]:
Mon
23
Tues
27
Wed
23
Thu
21
Fri
34

What was the average (mean) stock price for the week? (You may need to reference a built-in function)

In [7]:
mean(stock.prices)
Out[7]:
25.6

Create a vector called over.23 consisting of logicals that correspond to the days where the stock price was more than $23

In [8]:
over.23 <- stock.prices>23

Use the over.23 vector to filter out the stock.prices vector and only return the day and prices where the price was over $23

In [9]:
stock.prices[over.23]
Out[9]:
Tues
27
Fri
34

Use a built-in function to find the day the price was the highest

In [10]:
max(stock.prices)
Out[10]:
34

This didn't actually tell us the day! Only the max price, let's use a filter to grab the day!

In [15]:
max.price <- stock.prices == max(stock.prices)
max.price
Out[15]:
Mon
FALSE
Tues
FALSE
Wed
FALSE
Thu
FALSE
Fri
TRUE
In [16]:
stock.prices[max.price]
Out[16]:
Fri: 34

Okay that's it for the exercise on the basics! Great job!