coursera r programming week 2 assignment answers

• Coursera: R programming Week 2 Assignment
• by Lingyun Gao
• Last updated over 7 years ago
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R Programming Quiz 1 (JHU) Coursera

github repo for rest of specialization: Data Science Coursera

R was developed by statisticians working at...

The University of Auckland

The definition of free software consists of four freedoms (freedoms 0 through 3). Which of the following is NOT one of the freedoms that are part of the definition?

The freedom to sell the software for any price.

In R the following are all atomic data types EXCEPT

If I execute the expression x <- 4 in R, what is the class of the object 'x' as determined by the `class()' function?

What is the class of the object defined by x <- c(4, TRUE)?

If I have two vectors x <- c(1,3, 5) and y <- c(3, 2, 10), what is produced by the expression cbind(x, y)?

a 3 by 2 numeric matrix

A key property of vectors in R is that

elements of a vector all must be of the same class

Suppose I have a list defined as x <- list(2, "a", "b", TRUE). What does x[[1]] give me?

a numeric vector containing the element 2

Suppose I have a vector x <- 1:4 and a vector y <- 2. What is produced by the expression x + y?

a numeric vector with elements 3, 4, 5, 6.

Question 10

Suppose I have a vector x <- c(17, 14, 4, 5, 13, 12, 10) and I want to set all elements of this vector that are greater than 10 to be equal to 4. What R code achieves this?

x[x >= 11] <- 4

Question 11

In the dataset provided for this Quiz, what are the column names of the dataset?

Ozone, Solar.R, Wind, Temp, Month, Day

Question 12

Extract the first 2 rows of the data frame and print them to the console. What does the output look like?

Question 13

How many observations (i.e. rows) are in this data frame?

Question 14

Extract the last 2 rows of the data frame and print them to the console. What does the output look like?

Question 15

What is the value of Ozone in the 47th row?

Question 16

How many missing values are in the Ozone column of this data frame?

Question 17

What is the mean of the Ozone column in this dataset? Exclude missing values (coded as NA) from this calculation.

Explanation

The 'mean' function can be used to calculate the mean.

Question 18

Extract the subset of rows of the data frame where Ozone values are above 31 and Temp values are above 90. What is the mean of Solar.R in this subset?

Question 19

What is the mean of "Temp" when "Month" is equal to 6?

Question 20

What was the maximum ozone value in the month of May (i.e. Month = 5)?

Armbarbarian commented Apr 26, 2020

Thanks for this, so helpful. The course didn't go through a lot of the above code

Sorry, something went wrong.

Munim2001 commented May 4, 2020

Thank you so much for your help

Rgill800 commented May 7, 2020

Incredibly helpful

lekanfaye commented May 15, 2020

Thanks for your help, the 2nd part is not covered in the lecture

Arunan-R commented May 26, 2020

Thanks for the help. I went through the coursework twice but couldnt find how to do operations on the columns of the tables, This was very helpful!

Wainaina16 commented Jul 14, 2020

Thanks for the help

stocke777 commented Jul 18, 2020

coding part is right but not all

elbobbyjose commented Jul 24, 2020

Thanks my friend!

yashg008 commented Jul 28, 2020

thank you so much

omarabdelaz1z commented Aug 15, 2020

Very Helpful and kinda new commands for me, Thank you.

Dizartx commented Aug 17, 2020

DrDoofenshmirz commented Aug 26, 2020

thank u so much . some of the questions in the quiz require code that hasn't been taught yet in the course

Willto884 commented Sep 2, 2020

Very helpful... thank u very much...!

mastep25 commented Oct 10, 2020

Thank you very much for this help. You really contributed to my pass mark. Thanks

Sakshamgoel commented Dec 14, 2020

A big help to all who don't wanna buy the course but still want to learn.

jhw3 commented Jun 11, 2021

apply(sub, 2, max) what does the 2 represent in this?

sarahguagliardo commented Jun 23, 2021

I'm not entirely sure how to use the "apply" function yet, but I was able to get the same answers using commands like >mean(sub$Temp) after creating the subset correctly. The course doesn't go over the correct format for subsetting data very well so this quiz was really hard!

GarimaSodhi commented Jul 4, 2021

Thank you so much. This quiz was hard.

nizburfat commented Sep 15, 2021

Rating, Cocoa.Percent, and Company.Location. You decide to use the select() function to create a new data frame with only these three variables.

Assume the first part of your code is:

trimmed_flavors_df <- flavors_df %>%

Add the code chunk that lets you select the three variables.

trimmed_flavors_df %>%

You want to use the summarize() and mean() functions to find the mean rating for your data. Add the code chunk that lets you find the mean value for the variable Rating.

michaeladams01 commented Nov 17, 2021 • edited Loading

This came in so clutch. Thank you sir.

Krispeta commented Feb 9, 2022

I was so confused, looking everywhere, going back on the book and lessons, until I had to look for this! thank you, you saved the day, I was going bananas!!

bikrammajhi commented Oct 12, 2022 • edited Loading

Thank you for helping me out in my assignment. I initially panic since the question answer were not there in videos.

Divyam6969 commented Aug 31, 2023

thank youuu, this quiz was way tooo long lol

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R Programming Week 2: Assignment 1

Initialisation.

Configure evironment

The function ‘pollutantmean’ calculates the mean of a pollutant (sulfate or nitrate) across a specified list of monitors. The function ‘pollutantmean’ takes three arguments: ‘directory’, ‘pollutant’, and ‘id’. Given a vector monitor ID numbers, ‘pollutantmean’ reads that monitors’ particulate matter data from the directory specified in the ‘directory’ argument and returns the mean of the pollutant across all of the monitors, ignoring any missing values coded as NA.

The function ‘complete’ reads a directory full of files and reports the number of completely observed cases in each data file. The function should return a data frame where the first column is the name of the file and the second column is the number of complete cases.

The function ‘corr’ takes a directory of data files and a threshold for complete cases and calculates the correlation between sulfate and nitrate for monitor locations where the number of completely observed cases (on all variables) is greater than the threshold. The function should return a vector of correlations for the monitors that meet the threshold requirement. If no monitors meet the threshold requirement, then the function should return a numeric vector of length 0.

Q1. What value is returned by the following call to pollutantmean()? You should round your output to 3 digits.

Q2. What value is returned by the following call to pollutantmean()? You should round your output to 3 digits.

Q3. What value is returned by the following call to pollutantmean()? You should round your output to 3 digits.

Q4. What value is returned by the following call to pollutantmean()? You should round your output to 3 digits.

Q5. What value is printed at end of the following code?

Q6. What value is printed at end of the following code?

Q7. What value is printed at end of the following code?

Q8. What value is printed at end of the following code?

Q9. What value is printed at end of the following code?

Q10. What value is printed at end of the following code?