R类型3R语言矩阵
1R语言矩阵
我们使用包含数字元素的矩阵用于数学计算。
使用matrix()函数创建一个矩阵。matrix(data, nrow, ncol, byrow, dimnames)
以下是所使用的参数的说明 -
- 数据是成为矩阵的数据元素的输入向量。
- nrow是要创建的行数。
- ncol是要创建的列数。
- byrow是一个逻辑线索。 如果为TRUE，则输入向量元素按行排列。
- dimname是分配给行和列的名称
M <- matrix(c(3:14), nrow = 4, byrow = TRUE)//如果为TRUE，则输入向量元素按行排列。
print(M)
N <- matrix(c(3:14), nrow = 4, byrow = FALSE) //默认情况是这样的
print(N)
[,1] [,2] [,3]
[1,] 3 4 5
[2,] 6 7 8
[3,] 9 10 11
[4,] 12 13 14
[,1] [,2] [,3]
[1,] 3 7 11
[2,] 4 8 12
[3,] 5 9 13
[4,] 6 10 14
列分配给行和列的名称
# Define the column and row names.
rownames = c("row1", "row2", "row3", "row4")
colnames = c("col1", "col2", "col3")
P <- matrix(c(3:14), nrow = 4, byrow = TRUE, dimnames = list(rownames, colnames))
print(P)
col1 col2 col3
row1 3 4 5
row2 6 7 8
row3 9 10 11
row4 12 13 14
2访问矩阵的元素
# Access the element at 3rd column and 1st row. (顺序是y,x)
print(P[1,3])
# Access the element at 2nd column and 4th row.
print(P[4,2])
# Access only the 2nd row.
print(P[2,])
# Access only the 3rd column.
print(P[,3])
[1] 5
[1] 13
col1 col2 col3
6 7 8
row1 row2 row3 row4
5 8 11 14
3矩阵计算
使用R运算符对矩阵执行各种数学运算。 操作的结果也是一个矩阵。
对于操作中涉及的矩阵，维度（行数和列数）应该相同。
矩阵加法和减法
# Create two 2x3 matrices.
matrix1 <- matrix(c(3, 9, -1, 4, 2, 6), nrow = 2)
print(matrix1)
matrix2 <- matrix(c(5, 2, 0, 9, 3, 4), nrow = 2)
print(matrix2)
# Add the matrices.
result <- matrix1 + matrix2
cat("Result of addition","
")
print(result)
# Subtract the matrices
result <- matrix1 - matrix2
cat("Result of subtraction","
")
print(result)
[,1] [,2] [,3]
[1,] 3 -1 2
[2,] 9 4 6
[,1] [,2] [,3]
[1,] 5 0 3
[2,] 2 9 4
Result of addition
[,1] [,2] [,3]
[1,] 8 -1 5
[2,] 11 13 10
Result of subtraction
[,1] [,2] [,3]
[1,] -2 -1 -1
[2,] 7 -5 2
# Multiply the matrices.
result <- matrix1 * matrix2
cat("Result of multiplication","
")
print(result)
# Divide the matrices
result <- matrix1 / matrix2
cat("Result of division","
")
print(result)
Result of multiplication
[,1] [,2] [,3]
[1,] 15 0 6
[2,] 18 36 24
Result of division
[,1] [,2] [,3]
[1,] 0.6 -Inf 0.6666667
[2,] 4.5 0.4444444 1.5000000
