Convert an Object into a Matrix in R Programming – as.matrix() Function

as.matrix() Function in detail

The as.matrix() function in R is used to transform different types of objects into matrices. This is useful when working with structured data that needs to be handled in matrix form.

Syntax:

as.matrix(x)

Parameters:

x: The object that needs to be converted into a matrix.

Examples

Example 1: Converting a Vector to a Matrix

vector_data <- c(5:13)

# Convert the vector to a matrix
matrix_data <- as.matrix(vector_data)

# Print the matrix
print(matrix_data)

Output:

[,1]
[1, ]    5
[2, ]    6
[3, ]    7
[4, ]    8
[5, ]    9
[6, ]   10
[7, ]   11
[8, ]   12
[9, ]   13

Example 2: Converting a Data Frame to a Matrix

# Create a sample data frame
data_frame <- data.frame(Age = c(21, 25, 30, 35), Height = c(160, 170, 175, 180))

# Convert the data frame to a matrix
matrix_df <- as.matrix(data_frame)

# Print the matrix
print(matrix_df)

Properties:

• The total number of columns in the resultant matrix equals the sum of columns from the input matrices.
• Non-Commutative: The order in which matrices are combined matters, meaning cbind(A, B) ≠ cbind(B, A).
• Associative: cbind(cbind(A, B), C) = cbind(A, cbind(B, C)).

2. Row-Wise Combination

Row binding is done using the rbind() function in R. It merges two matrices, A_(m×p) and B_(n×p), row-wise, as long as they have the same number of columns.

Example:

# Create a sample data frame
data_frame <- data.frame(Age = c(21, 25, 30, 35), Height = c(160, 170, 175, 180))

# Convert the data frame to a matrix
matrix_df <- as.matrix(data_frame)

# Print the matrix
print(matrix_df)

Output:

Age Height
[1,]  21    160
[2,]  25    170
[3,]  30    175
[4,]  35    180

Example 3: Converting a Sparse Matrix to a Dense Matrix

library(Matrix)

# Create a sparse matrix
sparse_matrix <- Matrix(c(0, 3, 0, 0, 0, 7, 5, 0, 0), nrow = 3, ncol = 3)
print(sparse_matrix)

# Convert to a dense matrix
dense_matrix <- as.matrix(sparse_matrix)
print(dense_matrix)

Output:

3 x 3 sparse Matrix of class "dgCMatrix"
     [,1] [,2] [,3]
[1,]    0    3    0
[2,]    0    0    7
[3,]    5    0    0

     [,1] [,2] [,3]
[1,]    0    3    0
[2,]    0    0    7
[3,]    5    0    0

Example 4: Converting Coordinates to a Matrix

library(sp)

# Define coordinate points
coords <- cbind(c(10, 15, 20), c(25, 30, 35))

# Create a SpatialPointsDataFrame
spatial_df <- SpatialPointsDataFrame(coords = coords, data = data.frame(ID = 1:3))

# Convert the coordinates to a matrix
coord_matrix <- as.matrix(coords)

# Print the matrix
print(coord_matrix)

Output:

[,1] [,2]
[1,]   10   25
[2,]   15   30
[3,]   20   35