Filtering rows in R Programming - Step-by-Step Execution

Concept Flow - Filtering rows

Start with data frame

↓

Apply filter 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

Filtering rows means checking each row in a data frame and keeping only those that meet a condition.

Execution Sample

R Programming

df <- data.frame(x = 1:5, y = c(10, 20, 15, 5, 30))
filtered_df <- df[df$x > 2, ]
print(filtered_df)

This code keeps rows where the value in column x is greater than 2.

Execution Table

Step	Row Index	x Value	Condition (x > 2)	Keep Row?	Output Row
1	1	1	FALSE	No
2	2	2	FALSE	No
3	3	3	TRUE	Yes	3, 15
4	4	4	TRUE	Yes	4, 5
5	5	5	TRUE	Yes	5, 30
6	End				Filtering complete

💡 All rows checked; only rows with x > 2 are kept.

Variable Tracker

Variable	Start	After Step 3	After Step 4	After Step 5	Final
df$x	1,2,3,4,5	1,2,3,4,5	1,2,3,4,5	1,2,3,4,5	1,2,3,4,5
Condition (x > 2)	NA	FALSE, FALSE, TRUE, FALSE, FALSE	FALSE, FALSE, TRUE, TRUE, FALSE	FALSE, FALSE, TRUE, TRUE, TRUE	FALSE, FALSE, TRUE, TRUE, TRUE
filtered_df	NA	3, 15	3, 15; 4, 5	3, 15; 4, 5; 5, 30	3, 15; 4, 5; 5, 30

Key Moments - 2 Insights

Why do rows with x = 1 and x = 2 not appear in the filtered data?

Because their condition x > 2 is FALSE (see execution_table rows 1 and 2), so they are not kept.

What does the comma after df[df$x > 2, ] mean in R?

It means we are selecting rows where the condition is TRUE and keeping all columns. Omitting the comma (df[df$x > 2]) does the same and keeps all columns.

Visual Quiz - 3 Questions

Look at the execution_table, what is the condition result for row index 4?

A FALSE

B NA

C TRUE

D Error

💡 Hint

Check the 'Condition (x > 2)' column for row 4 in the execution_table.

At which step does the filtered data frame first include a row?

A Step 3

B Step 2

C Step 1

D Step 5

💡 Hint

Look at the 'Output Row' column in execution_table to see when rows start appearing.

If the condition changed to df$x >= 4, which row index would be kept first?

A 3

B 4

C 2

D 5

💡 Hint

Check variable_tracker for values of x and think which satisfy x >= 4.

Concept Snapshot

Filtering rows in R:
Use df[condition, ] to keep rows where condition is TRUE.
Condition checks each row's values.
Rows failing condition are dropped.
Comma after condition means keep all columns.
Result is a smaller data frame.

Full Transcript

Filtering rows means selecting only those rows in a data frame that meet a certain condition. In R, you write df[condition, ] where condition is a logical test on rows. Each row is checked: if the condition is TRUE, the row is kept; if FALSE, it is dropped. For example, df[df$x > 2, ] keeps rows where the x column is greater than 2. The comma after the condition means all columns are kept. The output is a new data frame with only the filtered rows.