The purpose of this assignment is to develop and assess your skills in R programming including summarising,
wrangling and plotting data. Using the tidyverse package is recommended but not compulsory. Please read
through the entire assignment and understand the submission format and marking rubrics before starting.
Part 1 [22 marks]
The spreadsheet titled ‘obesity.xlsx’ records the prevalence of obesity among adults in each country in the
world. Each sheet is supposed to record the information of each country in each year including the average
obesity rate and its 95% confidence interval of female, male and both groups. There were three years in the
given dataset (2006, 2011, and 2016). Another sheet called Continent with information about countries in
each continent is also given.
You will see that it is far from being ready for analysis and needs to be ‘wrangled’. Additionally, a few errors
have been deliberately introduced so these will need to be corrected by applying your R code.
1.1. Explain why the data in its current form is not considered to be in ‘tidy’ format. (1 mark)
1.2. Write a function that takes a year and outputs a data frame with one or more rows, where each row
shows the obesity rate of Male and Female in a country of that given year along with its 95%
confidence interval values. The returned dataframe should have 6 columns (Country, Year, Sex, Rate,
MinCI, MaxCI).
a) Load the data from the worksheet of the given year into a dataframe. (1 mark)
b) Drop the column ‘Both sexes’. (1 mark)
c) Add a new column named ‘Year’ filled all rows with the given year. (1 mark)
d) Use the gather() function to transform the data in the two columns Male and Female to become
rows. After this step, your dataframe now should have 4 columns: Country, Year, Sex, Rate.
(2 marks)
e) Split the Rate column into 3 columns named Rate, MinCI, MaxCI. Your dataframe should have 6
columns after this step: Country, Year, Sex, Rate, MinCI, MaxCI (2 marks)
f) Check and make necessary changes to make sure the data type of Rate, MinCI and MaxCI is
numeric. Print the summary of the dataframe. (1 mark)
g) Find and display rows with any invalid data, e.g. the rate value is not in the range of MinCI and
MaxCI, MinCI is larger than MaxCI, etc. If they exist, change the MinCI and MaxCI values in these
rows into NA. Print the summary of the dataframe. (2 marks)
h) Return the dataframe
1.3. Apply the function to each of the three years in the data to obtain three datasets then combine the
rows to form a single dataframe. Print the numbers of rows of the dataframe. (2 marks)
1.4. Query the dataframe obtained in 1.3 to print the average obesity rates of Female and Male of each
year. (2 marks)
1.5. Sort the dataframe obtained in 1.3 and display the country name, year, sex and rate in descending
order of obesity rates. Write the result to a csv file. (2 marks)
1.6. Load the data from the Continent worksheet into a dataframe, keeping only two columns, “Country
or area” and “Continent”. (1 mark)
1.7. Check if there is any country in the dataframe obtained in (1.3) not in the country list loaded in (1.6).
Display the country names if any (no duplicates). (2 marks)
1.8. Display the average obesity rate of Female in Europe and North America. (2 marks)

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