True/False and Multiple Choice

More than one answer may be possible.

1. T/F: A categorical variable assumes one of a few discrete values, and is usually saved in R as a factor or character vector.

2. T/F: If df is a tibble with a column called a, the following two commands produce the same output:

•  select(df,  a)

• df$a

3. The command df  %>%  filter(x  >  100,  y  <  20) is equivalent to which of the following:

a.  filter(df,  x  >  100,  y  <  20)

b.  filter(df,  x  >  100  &  y  <  20)

c.  filter(df,  x  >  100)  %>%  filter(df,  y  <  20)

d.  filter(df,  x  >  100)  &  filter(df,  y  <  20)

e.  df  %>%  filter(x  >  100)  %>%  filter(y  <  20)

4. I wish to sort df in descending order of column a, with ties broken by column b sorted in ascending order. Which of these commands would work?

a.  df  %>%  arrange(-a,  b)

b.  df  %>%  arrange(b,  desc(a))

c.  arrange(df,  -a,  -b)

d.  arrange(df,  desc(a),  b)

e.  None of these.

5.  I wish to drop all columns in df except for column a. Which of these commands would work?

a.  df  %>%  select(a)

b.  select(df,  -a)

c.  filter(df,  -a)

d.  filter(df,  a)

e. None of these.

Problems

1. The gss_cat dataset contains survey information from the General Social Survey. I used this dataset to create the following visualization showing the number of married versus non-married survey respondents:

a. In your opinion, is this an honest plot? Why or why not?

b. Generate a plot that more accurately depicts the number of married and non-married respondents in this survey.

2. Recreate the following plot which shows the how many miles were flown (across all departures) out of NYC-area airports by the top five most popular models of airplane:

3. The following table shows the proportion of flights which were delayed (either departure or arrival) by more than 60 minutes each month. Fill in the missing entries by providing code that generates the complete table.

4. Recall the a2weather dataset that we studied in lectures 4 and 5:      load(url("https://datasets.stats306.org/a2weather.RData "))

a) Here is a plot of the daily maximum temperature in Ann Arbor:

Suppose you are a climate researcher studying long-term warming trends in the Ann Arbor climate. Do you think this is a useful plot? Why or why not?

b) Produce a plot that more effectively depicts the long-term trend.