將矩陣組合到一個數組中R

Question

如果我有幾個我創建的矩陣，我怎樣才能將它們組合成一個數組？我有8個矩陣，每個矩陣有200行和200列，我需要將它們組合成一個dim = 200,200,8的數組。所以我希望每個矩陣都是我的數組的一部分。

Answer 1

這裏是兩個例子。你可以很容易地擴展這個八

# create two matricies with however many rows and columns 
x <- matrix(1:9 , 3 , 3) 
y <- matrix(10:18 , 3 , 3) 
# look at your starting data 
x 
y 

# store both inside an array, with the same first two dimensions, 
# but now with a third dimension equal to the number of matricies 
# that you are combining 
z <- array(c(x , y) , dim = c(3 , 3 , 2)) 

# result 
z 

Answer 2

如何：

combmat <- array(dim=c(200,200,8), data=cbind(matrix1,matrix2,...,matrix8)) 

Answer 3

可以使用abind函數從abind包：

library(abind) 
newarray <- abind(mat1, mat2, mat3, mat4, along=3) 

## or if mats are in a list (a good idea) 

newarray <- abind(matlist, along=3) 

Answer 4

這取決於你是否要結合他們列主要或行主要。這類似於使用cbind和rbind將矢量組合到矩陣中。因爲ř存儲在列主順序矩陣，這是最容易實現：

matrices <- list(
    matrix(1:9 , 3 , 3), 
    matrix(10:18 , 3 , 3) 
); 

#it is assumed all matrices in the list have equal dimensions 
array1 <- array(
    data = do.call(cbind, matrices), 
    dim = c(dim(matrices[[1]]), length(matrices)) 
); 

新的層面（2在這種情況下）將成爲第三維度。從打印方法的輸出來看，這看起來正確的，因爲它的最後一維分割打印：

> print(array1) 
, , 1 

    [,1] [,2] [,3] 
[1,] 1 4 7 
[2,] 2 5 8 
[3,] 3 6 9 

, , 2 

    [,1] [,2] [,3] 
[1,] 10 13 16 
[2,] 11 14 17 
[3,] 12 15 18 

不過，有時你可能需要將其由第一個維度，而不是相結合，如：

array2 <- array (
    data = do.call(rbind, lapply(matrices, as.vector)), 
    dim = c(length(matrices), dim(matrices[[1]])) 
); 

print(array2[1,,]) 

    [,1] [,2] [,3] 
[1,] 1 4 7 
[2,] 2 5 8 
[3,] 3 6 9 

例如，假設您想將這些矩陣分配給帶有列的數據框;每行一個矩陣。然後，第一尺寸，a.k.a nrow具有在陣列和數據幀以匹配：

mydf <- data.frame(foo = 1:2, row.names=c("first", "second")) 
mydf$bar <- array1 
    Error in `$<-.data.frame`(`*tmp*`, "bar", value = 1:18) : 
    replacement has 3 rows, data has 2 

mydf$bar <- array2 
mydf$bar 

Answer 5

下面是類似於abind -ing一個版本，但不使用任何額外的軟件包。收集一切都變成list，然後用sapply的選項simplify=到"array"，無爲列表中的每個部分後（identity剛剛返回的對象，等同於function(x) x）：

sapply(list(x,y), identity, simplify="array") 
# similarly to save a couple of keystrokes, the following is usually identical 
sapply(list(x,y), I, simplify="array") 

#, , 1 
# 
#  [,1] [,2] [,3] 
#[1,] 1 4 7 
#[2,] 2 5 8 
#[3,] 3 6 9 
# 
#, , 2 
# 
#  [,1] [,2] [,3] 
#[1,] 10 13 16 
#[2,] 11 14 17 
#[3,] 12 15 18 

如果你想保留每個原始矩陣的名字在新的陣列作爲標識符，嘗試：

sapply(mget(c("x","y")), identity, simplify="array") 

Answer 6

相關：How to stack multiple matrices in R

到目前爲止所有解決方案的問題是，當矩陣（不是data.frame s - 對於此dplyr和data.table工作正常）不具有相同的行和列順序時，綁定將堆疊彼此不相關的值。

如果您要檢查，並考慮到在每個維度的名字，看看narray：

（免責聲明：我寫的包）

Answer 7

library('abind') 
abind(m1, m2, m3, along = 2.5) 
abind(m1, m2, m3, along = 3) 

m4 <- list(m1, m2, m3) 
abind(m4, along = 3) 

     along  input = matrix + matrix      output 
---------------------------------------------------------------------------- 
     0   split columns and row bind them     array 
     0.5  same as 0          array 
     1   combine matrices into one matrix by rowwise  matrix 
     1.5  split columns and column bind them    array 
     2   combine matrices into one matrix by columnwise matrix 
     2.5  Form an array with matrices      array 
     3   Same as 2.5          array