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Learn Operations with Matrices | Matrices
R Introduction

bookOperations with Matrices

Matrices in R support arithmetic operations, both with single numbers and with built-in functions that summarize their values.

Scalar Operations

Applying an arithmetic operation with a single number affects every element in the matrix.

Example

1234
m <- matrix(1:9, nrow = 3, byrow = TRUE) # Multiply every element by 3 m * 3
copy

Aggregate Functions

Functions like sum() and mean() compute totals or averages across the entire matrix.

Example

123456
m <- matrix(1:9, nrow = 3, byrow = TRUE) # Overall mean of all elements mean(m) # Overall sum of all elements sum(m)
copy

Row and Column Functions

You can also apply these functions to rows or columns separately with rowSums(), rowMeans(), colSums(), and colMeans().

Example

123456
m <- matrix(1:9, nrow = 3, byrow = TRUE) # Column sums colSums(m) # Row means rowMeans(m)
copy

These functions make it easy to analyze matrix data by dimension.

Task

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You have a matrix named m:

2  4  6  8
10 12 14 16

Your tasks are:

  1. Divide each element by 2, then add 1. Reassign the result to the m variable.
  2. Output the matrix m.
  3. Output the column totals of the m matrix.
  4. Output the mean value of all m elements.

Solution

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Section 4. Chapter 6
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bookOperations with Matrices

Swipe to show menu

Matrices in R support arithmetic operations, both with single numbers and with built-in functions that summarize their values.

Scalar Operations

Applying an arithmetic operation with a single number affects every element in the matrix.

Example

1234
m <- matrix(1:9, nrow = 3, byrow = TRUE) # Multiply every element by 3 m * 3
copy

Aggregate Functions

Functions like sum() and mean() compute totals or averages across the entire matrix.

Example

123456
m <- matrix(1:9, nrow = 3, byrow = TRUE) # Overall mean of all elements mean(m) # Overall sum of all elements sum(m)
copy

Row and Column Functions

You can also apply these functions to rows or columns separately with rowSums(), rowMeans(), colSums(), and colMeans().

Example

123456
m <- matrix(1:9, nrow = 3, byrow = TRUE) # Column sums colSums(m) # Row means rowMeans(m)
copy

These functions make it easy to analyze matrix data by dimension.

Task

Swipe to start coding

You have a matrix named m:

2  4  6  8
10 12 14 16

Your tasks are:

  1. Divide each element by 2, then add 1. Reassign the result to the m variable.
  2. Output the matrix m.
  3. Output the column totals of the m matrix.
  4. Output the mean value of all m elements.

Solution

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Everything was clear?

How can we improve it?

Thanks for your feedback!

Section 4. Chapter 6
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