数组是R数据对象，可以在两个以上的维度存储数据.例如 : 如果我们创建一个维度数组(2,3,4)，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()函数创建数组.它将向量作为输入，并使用 dim 参数中的值来创建数组.
以下示例创建一个包含3个3列和3列的两个3x3矩阵的数组.
# 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
我们可以为行命名，数组中的列和矩阵使用 dimnames 参数.
# 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
# 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
由于数组是由多个维构成矩阵，对数组元素的操作是通过访问矩阵的元素来执行的.
# 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，会产生以下结果 : ;
[,1] [,2] [,3] [1,] 10 20 26 [2,] 18 22 28 [3,] 6 24 30
我们可以使用 apply()函数对数组中的元素进行计算.
apply(x, margin, fun)
以下是所用参数的描述 :
x 是一个数组.
margin 是所用数据集的名称.
fun 是要应用于整个数组的元素.
我们使用下面的apply()函数来计算al的数组行中元素的总和l矩阵.
# 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)
执行时上面的代码，它产生以下结果 :
, , 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
