[英]Accessing same matrix position from multiple matrices in a list in R?
I have a List of arbitrary length, all entries being matrices of arbitrary length and width but identically sized to each other.我有一个任意长度的列表,所有条目都是任意长度和宽度的矩阵,但彼此大小相同。 I would like to compute the mean, median, and mode of the values at the same position in every matrix in the list.
我想计算列表中每个矩阵中相同 position 值的平均值、中位数和众数。 I could do this with a for loop, but is there a simpler/vectorized way?
我可以用 for 循环来做到这一点,但有没有更简单/矢量化的方式?
I tried:我试过了:
for (x in 1:X){
for (y in 1:Y){
My_List[[B+1]][y,x] <- mean(My_List[[1:B]][y,x])
My_List[[B+2]][y,x] <- median(My_List[[1:B]][y,x])
My_List[[B+3]][y,x] <- mode(My_List[[1:B]][y,x])
}
}
Where the list is of length B+3, and the matrices are all of width X and length Y, but I got errors relating to trying to access across list entries.列表的长度为 B+3,矩阵的宽度均为 X,长度为 Y,但我遇到了与尝试跨列表条目访问有关的错误。 I considered lapply(), but I don't know how to turn a sunsetting operation into a FUN for the apply() family.
我考虑过 lapply(),但我不知道如何将日落操作变成 apply() 系列的乐趣。 I could do this with an obscene nest of for loops, but there must be a better way, especially in R.
我可以用一个淫秽的 for 循环嵌套来做到这一点,但必须有更好的方法,尤其是在 R 中。
EDIT: Reproducible example and expected output:编辑:可重现的示例和预期的 output:
Step 1: Generation of My_List:第 1 步:生成 My_List:
Matrix_A <- matrix(c(1, 2, 3, 4, 5, 6), nrow = 2)
Matrix_B <- matrix(c(2, 1, 3, 3, 6, 5), nrow = 2)
Matrix_C <- matrix(c(1, 1, 3, 3, 5, 5), nrow = 2)
# X = 3, Y = 2
B = 3
My_List <- vector(mode = "list", length = B + 3)
My_List[[1]] <- Matrix_A
My_List[[2]] <- Matrix_B
My_List[[3]] <- Matrix_C
My_List
Step 1 Output, note the NULL placeholder spaces:步骤 1 Output,注意 NULL 占位符空格:
[[1]]
[,1] [,2] [,3]
[1,] 1 3 5
[2,] 2 4 6
[[2]]
[,1] [,2] [,3]
[1,] 2 3 6
[2,] 1 3 5
[[3]]
[,1] [,2] [,3]
[1,] 1 3 5
[2,] 1 3 5
[[4]]
NULL
[[5]]
NULL
[[6]]
NULL
Using the same code block as above, I expect to see My_List[[4]][1,1] be the mean of My_List[[1]][1,1], My_List[[2]][1,1], and My_List[[3]][1,1], so 1 + 2 + 1 / 3 = 1.333, and so on for every combination of y and x.使用与上面相同的代码块,我希望看到 My_List[[4]][1,1] 是 My_List[[1]][1,1], My_List[[2]][1,1] 的平均值, 和 My_List[[3]][1,1],所以 1 + 2 + 1 / 3 = 1.333,对于 y 和 x 的每个组合,依此类推。 Index 4 of the list will be for mean, 5 for median, and 6 for mode.
列表的索引 4 表示平均值,5 表示中位数,6 表示众数。
I expect the final output to be:我希望最终的 output 是:
[[1]]
[,1] [,2] [,3]
[1,] 1 3 5
[2,] 2 4 6
[[2]]
[,1] [,2] [,3]
[1,] 2 3 6
[2,] 1 3 5
[[3]]
[,1] [,2] [,3]
[1,] 1 3 5
[2,] 1 3 5
[[4]] # Mean
[,1] [,2] [,3]
[1,] 1.333 3.000 5.333
[2,] 1.333 3.333 5.333
[[5]] # Median
[,1] [,2] [,3]
[1,] 1 3 5
[2,] 1 3 5
[[6]] # Mode
[,1] [,2] [,3]
[1,] 1 3 5
[2,] 1 3 5
You could transform the list of matrices to a 3 dimensional array:您可以将矩阵列表转换为 3 维数组:
i <- 2
j <- 3
n <- 4
# create list of n i*j matrices
l <- replicate(n, list(matrix(sample(10,i*j),i,j)))
# list to 3D array
arr.3d <- array(unlist(l), c(i, j, n))
apply(arr.3d, 1:2, mean)
[,1] [,2] [,3]
[1,] 6.50 5.00 3.50
[2,] 5.25 4.25 6.75
apply(arr.3d, 1:2,median)
[,1] [,2] [,3]
[1,] 6 5 1.5
[2,] 5 4 6.0
Mode <- function(x) {
ux <- unique(x)
ux[which.max(tabulate(match(x, ux)))]
}
apply(arr.3d,1:2,Mode)
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