Apply functions on matrices in R Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to calculate the sum of each row in the matrix.

R Programming

row_sums <- apply(matrix_data, [1], sum)

Drag options to blanks, or click blank then click option'

A1

B2

C3

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using margin 2 sums columns instead of rows.

Using margin 0 or 3 causes errors.

The apply function with margin 1 applies the function to rows.

2fill in blank

medium

Complete the code to calculate the mean of each column in the matrix.

R Programming

col_means <- apply(matrix_data, [1], mean)

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A3

B1

C2

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using margin 1 sums rows instead of columns.

Using margin 0 or 3 causes errors.

The apply function with margin 2 applies the function to columns.

3fill in blank

hard

Fix the error in the code to calculate the maximum value in each row.

R Programming

max_values <- apply(matrix_data, [1], max)

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A1

B0

C3

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Using margin 2 returns max per column instead.

Using margin 0 or 3 causes errors.

Margin 1 applies the function to rows, so use 1 to get max per row.

4fill in blank

hard

Fill both blanks to create a matrix of logical values where each element is TRUE if greater than 5.

R Programming

result <- apply(matrix_data, [1], function(x) x [2] 5)

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A2

B>

C<

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using margin 2 applies function column-wise, which is not intended here.

Using < or other operators changes the logic.

Margin 1 applies function to rows, and > checks if elements are greater than 5.

5fill in blank

hard

Fill all three blanks to create a named logical vector indicating which column sums are greater than 10.

R Programming

result <- sapply(colnames(matrix_data), function([1]) sum(matrix_data[ , [2]]) [3] 10)

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Acol

B>

C<

Drow

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of > changes the condition.

Using row instead of col causes indexing errors.

Use col as the variable name, > to check sums greater than 10, and col again to index columns.