Matrix dimensions in R Programming - Step-by-Step Execution

Concept Flow - Matrix dimensions

Create Matrix

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Check Dimensions

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Use dim() Function

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Get Rows and Columns

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Use Dimensions in Code

This flow shows how to create a matrix, check its dimensions using dim(), and then use those dimensions in your code.

Execution Sample

R Programming

m <- matrix(1:6, nrow=2, ncol=3)
dim(m)

Create a 2x3 matrix and get its dimensions.

Execution Table

Step	Action	Code	Result
1	Create matrix m with values 1 to 6, 2 rows, 3 columns	m <- matrix(1:6, nrow=2, ncol=3)	m = [ [1, 3, 5], [2, 4, 6] ]
2	Get dimensions of matrix m	dim(m)	2 3
3	Use dimensions to get number of rows	nrow(m)	2
4	Use dimensions to get number of columns	ncol(m)	3

💡 All steps complete, matrix dimensions retrieved successfully.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4
m	NULL	[[1, 3, 5], [2, 4, 6]]	[[1, 3, 5], [2, 4, 6]]	[[1, 3, 5], [2, 4, 6]]	[[1, 3, 5], [2, 4, 6]]
dim(m)	NULL	NULL	[2, 3]	[2, 3]	[2, 3]
nrow(m)	NULL	NULL	NULL	2	2
ncol(m)	NULL	NULL	NULL	NULL	3

Key Moments - 2 Insights

Why does dim(m) return a vector with two numbers?

dim(m) returns two numbers because it gives the number of rows first, then the number of columns, as shown in step 2 of the execution_table.

Is the matrix filled by rows or columns when created with matrix(1:6, nrow=2, ncol=3)?

By default, R fills the matrix by columns, so numbers go down each column first, as seen in the matrix m after step 1.

Visual Quiz - 3 Questions

Look at the execution_table, what is the output of dim(m) at step 2?

A [2, 3]

B [3, 2]

C [6]

D NULL

💡 Hint

Check the 'Result' column in row for step 2 in execution_table.

At which step do we get the number of rows of the matrix?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'Action' column describing getting number of rows.

If we change nrow=3 and ncol=2 in matrix creation, what will dim(m) return?

A [2, 3]

B [3, 2]

C [6, 1]

D [1, 6]

💡 Hint

dim(m) returns rows then columns, so changing nrow and ncol swaps those values.

Concept Snapshot

Matrix dimensions in R:
- Use matrix(data, nrow, ncol) to create.
- Use dim(matrix) to get rows and columns as a vector.
- Use nrow(matrix) and ncol(matrix) for separate values.
- R fills matrices by columns by default.

Full Transcript

This visual execution shows how to create a matrix in R with specific rows and columns, then how to get its dimensions using dim(). The matrix m is created with values 1 to 6, arranged in 2 rows and 3 columns. The dim() function returns a vector with two numbers: the number of rows and the number of columns. We also see how to get the number of rows and columns separately using nrow() and ncol(). This helps understand how matrix dimensions work in R.