Data Wrangling 1
Bora Jin
Material
🎥 Watch Tidy Data
🎥 Watch Grammar of Data Wrangling
🎥 Watch Working With a Single Data Frame
Today's Goal
- Understand how data are organized according to a consistent set of "tidy" principles
- Use seven key verbs to wrangle data and extract meaning
"Happy families are all alike; every unhappy family is unhappy in its own way" - Leo Tolstoy
Quiz
Tidy data has three related characteristics
- Each variable forms a column.
- Each observation forms a row.
- Each value has its own cell.
Quiz
Tidy data has three related characteristics
- Each variable forms a column.
- Each observation forms a row.
- Each value has its own cell.
Q - A tidy data set is tidy for any analyses (T/F).
Quiz
Tidy data has three related characteristics
- Each variable forms a column.
- Each observation forms a row.
- Each value has its own cell.
Q - A tidy data set is tidy for any analyses (T/F).
F
Quiz
Q - What makes this data not tidy?
source: https://gist.github.com/Kimmirikwa/b69d0ea134820ea52f8481991ffae93e#file-student_results-csv
Quiz
Q - What makes this data not tidy?
sex and age: multiple variables in one columntest number: not a value for each observation,test 1andtest 2should be a variableterm 1-3: can be aggregated
| id | name | phone | sex | age | test1 | test2 | term |
|---|---|---|---|---|---|---|---|
| 1 | Mike | 134 | m | 12 | 76 | 85 | term1 |
| 1 | Mike | 134 | m | 12 | 84 | 80 | term2 |
| 1 | Mike | 134 | m | 12 | 87 | 90 | term3 |
Quiz
Q - Correct the following sentences about dplyr functions:
a. Its input can be a matrix.
b. Its output is in various forms.
c. Functions are nouns.
d. Replace the input data frame.
Quiz
Q - Correct the following sentences about dplyr functions:
a. Its input should be a data frame.
b. Its output is always a data frame.
c. Functions are verbs.
d. Do not modify the input data frame.
Quiz
Q - Whic of these is the most appropriate translation of %>% in English?
a. Before
b. Which
c. Then
d. Do
Quiz
Q - What of these is the most appropriate translation of %>% in English?
a. Before
b. Which
c. Then
d. Do
Quiz
Q - Connect each function to its effect.
filter -
arrange -
select -
distinct -
mutate -
summarize -
group_by -
pick columns by variable names
reorder rows by values of variables
pick rows matching criteria
enable grouped operations
compute summary statistics
extract unique rows
create new variables
Bulletin
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