filter() for row selection in R Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the filter() function do in R?

It selects rows from a data frame that meet a specific condition, like picking only the apples from a basket of fruits.

beginner

How do you use filter() to select rows where a column age is greater than 30?

Use filter(data, age > 30). This keeps only rows where the age is more than 30.

intermediate

Can filter() handle multiple conditions? How?

Yes! Use commas or logical operators like & or |. For example, filter(data, age > 30, gender == 'F') selects rows where age is over 30 AND gender is female.

beginner

What package do you need to use filter() for data frames?

The dplyr package. It makes data manipulation easy and clear.

beginner

What happens if no rows meet the condition in filter()?

You get an empty data frame with the same columns but zero rows, like an empty basket after picking fruits.

Which function is used to select rows based on conditions in R's dplyr package?

A mutate()

B select()

C arrange()

D filter()

filter() selects rows by condition. select() chooses columns, arrange() sorts rows, and mutate() adds or changes columns.

What will filter(data, age > 25, gender == 'M') do?

A Select rows where age is over 25 and gender is male

B Select rows where age is over 25 or gender is male

C Select rows where age is under 25 and gender is male

D Select all rows

Using commas means AND condition, so both must be true.

If no rows match the filter condition, what does filter() return?

A An empty data frame with zero rows

B The original data frame

C An error

D NULL

filter() returns an empty data frame with the same columns but no rows.

Which package must be loaded to use filter() for data frames?

A ggplot2

B dplyr

C tidyr

D base

dplyr provides filter() for easy row selection.

How do you combine multiple conditions inside filter()?

A Using parentheses only

B Using plus signs (+)

C Using commas or logical operators like && and |

D Using semicolons (;)

Commas act like AND, and logical operators combine conditions logically.

Explain how to use filter() to select rows from a data frame based on one or more conditions.

Think about how you pick only certain fruits from a basket based on color or size.

What happens when filter() finds no rows matching the condition? How can this be useful?

Imagine looking for red apples but finding none.