Week 3 Drill

Don’t Peek!

Here are the first letters of the names of several data verbs. (Repeated letters are for different verbs.) Complete the name and say briefly what the verb does.

Rather than looking at a list of verbs, do this just from memory.

• A
• G
• J
• M
• F
• S
• S

Data verbs and their uses

Each of these tasks can be performed using a single data verb. For each task, say which verb it is:

• Find the average of one of the variables.

summarise()

• Add a new column that is the ratio between two variables.

mutate()

• Sort the cases in descending order of a variable.

arrange()

• Create a new data table that includes only those cases that meet a criterion.

filter()

• From a data table with three categorical variables A, B, & C, and a quantitative variable X, produce an output that has a separate case for each of the combinations of the levels of A and B. (Hint: It might be easier to see the answer if the problem statement added, “and gives the maximum value of X over all the cases that have a given combination of A and B.” )

filter()

• From a data table with three categorical variables A, B, & C, and a quantitative variable X, produce an output that has the same cases but only the variables A and X.

Two steps

These questions refer to the diamonds data table. Take a look at the codebook (using help()) so that you’ll understand the meaning of the tasks.¹

Each of the following tasks can be accomplished by a statement of the form

diamonds %>% 
  verb1( args1 ) %>% 
  verb2( args2 ) %>% 
  arrange( args3 ) %>% head( 1 )

Identify the verbs and arguments.

1. Which color diamonds seem to be largest on average (in terms of carats)?
   • verb1:
   • verb2:
   • args1:
   • args2:
   • args3:
2. Which clarity of diamonds has the largest average “table” per carat?
   • verb1:
   • verb2:
   • args1:
   • args2:
   • args3:
3. What color of diamonds occurs the most frequently among diamonds with ideal cuts?
   • verb1:
   • verb2:
   • args1:
   • args2:
   • args3:
4. What is the average price per carat of diamonds that cost more than $10000?
   • verb1:
   • verb2:
   • args1:
   • args2:
   • args3:
5. Create a new data set that groups diamonds by color and displays the average depth and average table for each group.
   • verb1:
   • verb2:
   • args1:
   • args2:
   • args3:

Tables

Here is a small data table based on BabyNames. Take this table as the input.

name	sex	count	year
Christina	M	22	1967
Rotha	F	7	1907
Wayman	M	9	1997
Song	F	11	1994
Julian	M	535	1948
Vicky	F	2945	1957
Kalia	F	46	1989
Lissa	F	102	1962
Brand	M	10	1991
Josedejesus	M	9	1985

Just by chance, this small sample pulled out the listing for Christina males.

Task

For each of the following outputs, identify the operation and write down the details of the operation.

• Output Table 1

name	sex	count	year
Rotha	F	7	1907
Song	F	11	1994
Kalia	F	46	1989
Lissa	F	102	1962
Vicky	F	2945	1957
Wayman	M	9	1997
Josedejesus	M	9	1985
Brand	M	10	1991
Christina	M	22	1967
Julian	M	535	1948

• Output Table 2

name	sex	count	year
Rotha	F	7	1907
Song	F	11	1994
Vicky	F	2945	1957
Kalia	F	46	1989
Lissa	F	102	1962

• Output Table 3

name	sex	count	year
Christina	M	22	1967
Julian	M	535	1948

• Output Table 4

total
3696

• Output Table 5

name	count
Christina	22
Rotha	7
Wayman	9
Song	11
Julian	535
Vicky	2945
Kalia	46
Lissa	102
Brand	10
Josedejesus	9

Changing Cases

There’s only one data verb that takes a single data table as input and produce an output that (in general) has a different meaning to the case. Which one?

summarise()

There’s only one data verb that takes two data tables as input rather than just a single data table. Which one?

join()

Please use the comment system to make suggestions, point out errors, or to discuss the topic.

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1. Motivated by this problem set based on drills by Garrett Grolemund which are licensed under the CC Attribution-Noncommercial-Share Alike 3.0 License.↩