Arrays

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2023-12-01

数组是R数据对象,可以存储两个以上的数据。 例如 - 如果我们创建一个维度(2,3,4)数组,那么它会创建4个矩形矩阵,每个矩阵有2行3列。 数组只能存储数据类型。

使用array()函数创建array() 。 它将矢量作为输入,并使用dim参数中的值来创建数组。

例子 (Example)

以下示例创建一个包含两个3x3矩阵的数组,每个矩阵包含3行和3列。

# Create two vectors of different lengths.
vector1 <- c(5,9,3)
vector2 <- c(10,11,12,13,14,15)
# Take these vectors as input to the array.
result <- array(c(vector1,vector2),dim = c(3,3,2))
print(result)

当我们执行上面的代码时,它会产生以下结果 -

, , 1
     [,1] [,2] [,3]
[1,]    5   10   13
[2,]    9   11   14
[3,]    3   12   15
, , 2
     [,1] [,2] [,3]
[1,]    5   10   13
[2,]    9   11   14
[3,]    3   12   15

命名列和行

我们可以使用dimnames参数为数组中的行,列和矩阵dimnames

# Create two vectors of different lengths.
vector1 <- c(5,9,3)
vector2 <- c(10,11,12,13,14,15)
column.names <- c("COL1","COL2","COL3")
row.names <- c("ROW1","ROW2","ROW3")
matrix.names <- c("Matrix1","Matrix2")
# Take these vectors as input to the array.
result <- array(c(vector1,vector2),dim = c(3,3,2),dimnames = list(row.names,column.names,
   matrix.names))
print(result)

当我们执行上面的代码时,它会产生以下结果 -

, , Matrix1
     COL1 COL2 COL3
ROW1    5   10   13
ROW2    9   11   14
ROW3    3   12   15
, , Matrix2
     COL1 COL2 COL3
ROW1    5   10   13
ROW2    9   11   14
ROW3    3   12   15

访问数组元素 (Accessing Array Elements)

# Create two vectors of different lengths.
vector1 <- c(5,9,3)
vector2 <- c(10,11,12,13,14,15)
column.names <- c("COL1","COL2","COL3")
row.names <- c("ROW1","ROW2","ROW3")
matrix.names <- c("Matrix1","Matrix2")
# Take these vectors as input to the array.
result <- array(c(vector1,vector2),dim = c(3,3,2),dimnames = list(row.names,
   column.names, matrix.names))
# Print the third row of the second matrix of the array.
print(result[3,,2])
# Print the element in the 1st row and 3rd column of the 1st matrix.
print(result[1,3,1])
# Print the 2nd Matrix.
print(result[,,2])

当我们执行上面的代码时,它会产生以下结果 -

COL1 COL2 COL3 
   3   12   15 
[1] 13
     COL1 COL2 COL3
ROW1    5   10   13
ROW2    9   11   14
ROW3    3   12   15

操纵数组元素

由于数组由多维构成矩阵,因此通过访问矩阵的元素来执行对数组元素的操作。

# Create two vectors of different lengths.
vector1 <- c(5,9,3)
vector2 <- c(10,11,12,13,14,15)
# Take these vectors as input to the array.
array1 <- array(c(vector1,vector2),dim = c(3,3,2))
# Create two vectors of different lengths.
vector3 <- c(9,1,0)
vector4 <- c(6,0,11,3,14,1,2,6,9)
array2 <- array(c(vector1,vector2),dim = c(3,3,2))
# create matrices from these arrays.
matrix1 <- array1[,,2]
matrix2 <- array2[,,2]
# Add the matrices.
result <- matrix1+matrix2
print(result)

当我们执行上面的代码时,它会产生以下结果 -

     [,1] [,2] [,3]
[1,]   10   20   26
[2,]   18   22   28
[3,]    6   24   30

跨数组元素的计算

我们可以使用apply()函数对数组中的元素进行计算。

语法 (Syntax)

apply(x, margin, fun)

以下是所用参数的说明 -

  • x是一个数组。

  • margin是使用的数据集的名称。

  • fun是要跨数组元素应用的函数。

例子 (Example)

我们使用下面的apply()函数计算所有矩阵中数组行中元素的总和。

# Create two vectors of different lengths.
vector1 <- c(5,9,3)
vector2 <- c(10,11,12,13,14,15)
# Take these vectors as input to the array.
new.array <- array(c(vector1,vector2),dim = c(3,3,2))
print(new.array)
# Use apply to calculate the sum of the rows across all the matrices.
result <- apply(new.array, c(1), sum)
print(result)

当我们执行上面的代码时,它会产生以下结果 -

, , 1
     [,1] [,2] [,3]
[1,]    5   10   13
[2,]    9   11   14
[3,]    3   12   15
, , 2
     [,1] [,2] [,3]
[1,]    5   10   13
[2,]    9   11   14
[3,]    3   12   15
[1] 56 68 60