Modifying and adding elements in R Programming - Step-by-Step Execution

Concept Flow - Modifying and adding elements

Start with vector

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Access element by index

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Modify element value

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Add new element

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Resulting vector updated

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End

This flow shows how to access and change elements in a vector, then add new elements to it.

Execution Sample

R Programming

vec <- c(10, 20, 30)
vec[2] <- 25
vec <- c(vec, 40)
print(vec)

This code changes the second element of a vector and adds a new element at the end.

Execution Table

Step	Action	Vector State	Output
1	Create vector vec with c(10, 20, 30)	[10, 20, 30]
2	Modify vec[2] to 25	[10, 25, 30]
3	Add new element 40 with c(vec, 40)	[10, 25, 30, 40]
4	Print vec	[10, 25, 30, 40]	10 25 30 40

💡 All steps completed, vector modified and new element added.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
vec	NULL	[10, 20, 30]	[10, 25, 30]	[10, 25, 30, 40]	[10, 25, 30, 40]

Key Moments - 2 Insights

Why does vec[2] <- 25 change only the second element?

Because vec[2] accesses the second element directly, so assigning 25 replaces only that element (see execution_table step 2).

How does c(vec, 40) add a new element instead of replacing?

c(vec, 40) combines the existing vector with 40, creating a longer vector (see execution_table step 3).

Visual Quiz - 3 Questions

Look at the execution table, what is the vector after step 2?

A [10, 20, 30]

B [10, 25, 30]

C [10, 25, 30, 40]

D [25, 20, 30]

💡 Hint

Check the 'Vector State' column at step 2 in the execution_table.

At which step is the new element 40 added to the vector?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look for the action mentioning c(vec, 40) in the execution_table.

If we changed vec[2] <- 25 to vec[2] <- 50, what would be the vector after step 2?

A [10, 50, 30]

B [10, 20, 30]

C [10, 25, 30]

D [50, 20, 30]

💡 Hint

Refer to how vec[2] is assigned in step 2 and imagine the new value.

Concept Snapshot

Modifying and adding elements in R vectors:
- Use vec[index] <- value to change an element.
- Use c(vec, new_element) to add elements.
- Indexing starts at 1.
- Vector length grows when adding elements.
- Changes update the original vector variable.

Full Transcript

This lesson shows how to change and add elements in an R vector. We start with a vector of three numbers. Then we change the second number by accessing it with vec[2] and assigning a new value. Next, we add a new number at the end by combining the vector with the new element using c(vec, 40). Finally, we print the updated vector. Each step updates the vector, and the changes are shown clearly in the execution table and variable tracker.