filter() for row selection in R Programming - Step-by-Step Execution

Concept Flow - filter() for row selection

Start with data frame

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Apply filter() with condition

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Check each row against condition

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Keep rows where condition is TRUE

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Return filtered data frame

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End

The filter() function checks each row of a data frame against a condition and keeps only the rows where the condition is true.

Execution Sample

R Programming

library(dplyr)
data <- data.frame(name=c("Anna", "Bob", "Cara"), age=c(25, 30, 22))
young <- filter(data, age < 30)
print(young)

This code selects rows from 'data' where 'age' is less than 30 and prints the filtered data.

Execution Table

Step	Row	Condition (age < 30)	Keep Row?	Output Rows So Far
1	1 (Anna, 25)	25 < 30 is TRUE	Yes	Anna, 25
2	2 (Bob, 30)	30 < 30 is FALSE	No	Anna, 25
3	3 (Cara, 22)	22 < 30 is TRUE	Yes	Anna, 25; Cara, 22
4	End	-	-	Filtering complete

💡 All rows checked; rows with age < 30 kept.

Variable Tracker

Variable	Start	After Row 1	After Row 2	After Row 3	Final
data	[Anna,25; Bob,30; Cara,22]	[Anna,25; Bob,30; Cara,22]	[Anna,25; Bob,30; Cara,22]	[Anna,25; Bob,30; Cara,22]	[Anna,25; Bob,30; Cara,22]
young	empty	[Anna,25]	[Anna,25]	[Anna,25; Cara,22]	[Anna,25; Cara,22]

Key Moments - 2 Insights

Why does the row with Bob (age 30) not appear in the output?

Because the condition 'age < 30' is FALSE for Bob (30 < 30 is FALSE), so filter() excludes that row as shown in execution_table step 2.

Does filter() change the original data frame?

No, filter() returns a new data frame with selected rows. The original 'data' remains unchanged as shown in variable_tracker.

Visual Quiz - 3 Questions

Look at the execution_table at step 3. Which rows are kept after checking Cara?

A Anna and Cara

B Anna, Bob, and Cara

C Only Anna

D Only Cara

💡 Hint

Check the 'Output Rows So Far' column at step 3 in execution_table.

At which step does the condition become FALSE for a row?

A Step 3

B Step 1

C Step 2

D No FALSE condition

💡 Hint

Look at the 'Condition (age < 30)' column in execution_table for each step.

If we change the condition to age <= 30, what happens to the output?

A Bob's row is excluded

B Bob's row is included

C Only Cara's row is included

D No rows are included

💡 Hint

Consider how the condition changes and check execution_table logic for age comparisons.

Concept Snapshot

filter(data, condition)
- Checks each row in 'data'
- Keeps rows where 'condition' is TRUE
- Returns a new filtered data frame
- Original data stays unchanged
- Useful for selecting rows by criteria

Full Transcript

The filter() function in R is used to select rows from a data frame that meet a certain condition. It checks each row one by one. If the condition is true for that row, the row is kept. If not, it is skipped. The result is a new data frame with only the rows that passed the test. The original data frame does not change. For example, filtering rows where age is less than 30 keeps only those rows with age under 30. This is shown step-by-step in the execution table and variable tracker.