Adding and removing columns in R Programming - Step-by-Step Execution

Concept Flow - Adding and removing columns

Start with data frame

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Add column: df$new_col <- values

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Check data frame with new column

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Remove column: df$new_col <- NULL

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Check data frame after removal

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End

Start with a data frame, add a new column by assigning values, then remove a column by setting it to NULL.

Execution Sample

R Programming

df <- data.frame(a = 1:3, b = 4:6)
df$c <- c(7,8,9)
df$c <- NULL
print(df)

Create a data frame, add a column 'c', then remove it, and print the final data frame.

Execution Table

Step	Action	Data Frame Columns	Details
1	Create df with columns a and b	a, b	df = data.frame(a=1:3, b=4:6)
2	Add column c	a, b, c	df$c <- c(7,8,9) adds new column c
3	Remove column c	a, b	df$c <- NULL removes column c
4	Print df	a, b	Final df has columns a and b only

💡 No more steps; column c was added then removed.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
df columns	none	a, b	a, b, c	a, b	a, b

Key Moments - 2 Insights

Why does setting df$c to NULL remove the column?

In R, assigning NULL to a data frame column deletes that column, as shown in step 3 of the execution_table.

What happens if you add a column with a different length than existing columns?

R will give an error or recycle values; in this example, lengths match so no error occurs (step 2).

Visual Quiz - 3 Questions

Look at the execution_table, after which step does the data frame have three columns?

A After Step 2

B After Step 1

C After Step 3

D After Step 4

💡 Hint

Check the 'Data Frame Columns' column in execution_table rows.

At the final step, which columns remain in the data frame?

A a, b, c

B a only

C a, b

D c only

💡 Hint

Look at the 'Final' column in variable_tracker and last row in execution_table.

If you skip step 3 (removing column c), what would the final data frame columns be?

A a, b

B a, b, c

C c only

D none

💡 Hint

Refer to step 2 in execution_table where column c is added.

Concept Snapshot

Adding columns: df$new_col <- values
Removing columns: df$col <- NULL
Data frame updates immediately
Column lengths must match or recycle
Use print(df) to see changes

Full Transcript

This example shows how to add and remove columns in an R data frame. First, we create a data frame df with columns a and b. Then, we add a new column c by assigning a vector to df$c. Next, we remove column c by setting df$c to NULL. Finally, we print the data frame to see that only columns a and b remain. Assigning NULL to a column deletes it. Column lengths should match existing rows to avoid errors. This step-by-step trace helps beginners see how the data frame changes after each operation.