Intro to Data Science - HW 1

Copyright Jeffrey Stanton, Jeffrey Saltz, and Jasmina Tacheva

# Enter your name here: Diganta Rashed

Attribution statement: (choose only one and delete the rest)

# 1. I did this homework by myself, with help from the book and the professor.
# 2. I did this homework with help from the book and the professor and these Internet sources:
# 3. I did this homework with help from <Name of another student> but did not cut and paste any code.

Define a variable:

x <- 280

Define the following vectors, which represent the population (in thousands) and number of colleges in each of the five counties in Central New York (CNY) – Cayuga, Cortland, Madison, Onondaga, and Oswego, in this order:

population <- c(80, 49, 73, 467, 122)
colleges <- c(2, 2, 3, 9, 2)

Part 1: Calculating statistics using R

1. Show the number of observations in the population vector with the length() function:

length(population)

## [1] 5

2. Show the number of observations in the colleges vector with the length() function:

length(colleges)

## [1] 5

3. Calculate the average CNY population using the mean() function:

mean(population)

## [1] 158.2

4. Calculate the average number of colleges in CNY using the mean() function:

mean(colleges)

## [1] 3.6

5. Calculate the total CNY population using the sum() function:

sum(population)

## [1] 791

6. Calculate the total number of colleges in CNY using the sum() function:

sum(colleges)

## [1] 18

7. Calculate the average CNY population again, this time using the results from steps A & E:

mean(791/5)

## [1] 158.2

8. Calculate the average number of colleges in CNY again, this time using the results from steps B & F:

mean(18/5)

## [1] 3.6

Part 2: Using the max/min and range functions in {r}

1. How many colleges does the county with most colleges have? Hint: Use the max() function:

max(colleges)

## [1] 9

10. What is the population of the least populous county in CNY? Hint: Use the min() function:

min(population)

## [1] 49

11. Display the populations of the least populous and most populous county in the dataset together. Hint: Use the range() function:

range(population)

## [1]  49 467

Part 3: Vector Math

12. Create a new vector called extraPop, which is the current population of a county + 50 (each county has 50,000 more people):

extraPop <- c(population +50)

13. Calculate the average of extraPop:

mean(extraPop)

## [1] 208.2

14. In a variable called bigCounties, store all the population numbers from the original population vector which are greater than 120 (using subsetting in R):

bigCounties <- population[population >120]

15. Report the length of bigCounties:

length(bigCounties)

## [1] 2