Indexing in Matrices
Matrix elements are accessed with two indices: the row number and the column number. As usual, indexing starts at 1. Use square brackets [row, column] to specify the position of an element.
Single Elements
Provide both a row and a column index to extract a single value.
Example
1234567num <- 1:9 m <- matrix(num, nrow = 3, ncol = 3, byrow = T) # Element in row 2, column 2 (value 5) m[2, 2] # Element in row 1, column 3 (value 3) m[1, 3]
Multiple Elements
Use a vector of indices to extract multiple values at once.
Example
12345num <- 1:9 m <- matrix(num, nrow = 3, ncol = 3, byrow = T) # Elements in row 3, columns 2 and 3 m[3, c(2, 3)]
Entire Rows or Columns
Omit one of the indices to return a full row or column.
Example
1234567num <- 1:9 m <- matrix(num, nrow = 3, ncol = 3, byrow = T) # Entire first row m[1, ] # Entire third column m[, 3]
Swipe to start coding
You have a matrix named m:
2 4 6 8
10 12 14 16
Your tasks are to:
- Extract the element
12. - Extract the elements
4 6. - Extract the third column.
Рішення
Дякуємо за ваш відгук!
single
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Matrix elements are accessed with two indices: the row number and the column number. As usual, indexing starts at 1. Use square brackets [row, column] to specify the position of an element.
Single Elements
Provide both a row and a column index to extract a single value.
Example
1234567num <- 1:9 m <- matrix(num, nrow = 3, ncol = 3, byrow = T) # Element in row 2, column 2 (value 5) m[2, 2] # Element in row 1, column 3 (value 3) m[1, 3]
Multiple Elements
Use a vector of indices to extract multiple values at once.
Example
12345num <- 1:9 m <- matrix(num, nrow = 3, ncol = 3, byrow = T) # Elements in row 3, columns 2 and 3 m[3, c(2, 3)]
Entire Rows or Columns
Omit one of the indices to return a full row or column.
Example
1234567num <- 1:9 m <- matrix(num, nrow = 3, ncol = 3, byrow = T) # Entire first row m[1, ] # Entire third column m[, 3]
Swipe to start coding
You have a matrix named m:
2 4 6 8
10 12 14 16
Your tasks are to:
- Extract the element
12. - Extract the elements
4 6. - Extract the third column.
Рішення
Перейдіть на комп'ютер для реальної практикиПродовжуйте з того місця, де ви зупинились, використовуючи один з наведених нижче варіантівДякуємо за ваш відгук!
single
