R語言數組
數組是可以在二維及以上存儲數據的R數據對象。 例如 - 如果創建一個維數組(2,3,4)，那麼它將創建4個矩形矩陣，每個矩陣具有2行和3列。數組只能存儲數據類型。
數組可通過使用array()函數來創建。 它將向量作爲輸入，並使用dim參數中的值來創建數組。
例子
以下示例創建兩個3x3矩陣的數組，每個矩陣具有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)當我們執行上述代碼時，會產生以下結果 -
, , 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
可以使用dimnames參數爲數組中的行，列和矩陣命名。
# 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)當我們執行上述代碼時，會產生以下結果 -
, , 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訪問數組元素
有關如何訪問數組元素，請參考以下代碼實現 -
# 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])當我們執行上述代碼時，會產生以下結果 -
COL1 COL2 COL3
3 12 15
[1] 13
COL1 COL2 COL3
ROW1 5 10 13
ROW2 9 11 14
ROW3 3 12 15操縱數組元素
由於數組是由多個維度組成的矩陣，通過訪問矩陣的元素來執行數組元素的相關操作。
# 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)當我們執行上述代碼時，會產生以下結果 -
[,1] [,2] [,3]
[1,] 10 20 26
[2,] 18 22 28
[3,] 6 24 30跨數組元素的計算
我們可以使用apply()函數對數組中的元素進行計算。
語法
apply(x, margin, fun)以下是使用的參數的描述 -
- x - 是一個數組。
- margin - 是使用的數據集的名稱。
- fun - 是應用於數組元素的函數。
例子
使用下面的apply()函數來計算所有矩陣中數組的行中的元素的總和。
# 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)當我們執行上述代碼時，會產生以下結果 -
, , 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