R中列表对象之间的矩阵计算

Question

我在 R 中创建了如下对象列表：

set.seed(1234)
data <- matrix(rnorm(3*4,mean=0,sd=1), 3, 4) 
results <- lapply(1:ncol(data), function(i) outer(data[, i], data[, i]))

所有 4 个列表对象都有 dim=3x3。我还有以下矩阵matr <- matrix(c(2,4,6,8),ncol=4)，其中每个值对应于上面的列表对象。

然后，我在前两个对象之间使用这个等式 matr[,1]*matr[,2]*results[[1]]*results[[2]] 以创建下面的矩阵

          [,1]      [,2]       [,3]
[1,] 64.135122 2.6966755 12.4307531
[2,]  2.696676 0.1133865  0.5226732
[3,] 12.430753 0.5226732  2.4093448

如何为所有可能的对象组合计算上述等式并将它们保存到新列表？

Answer 1

我们可以使用combn在list的序列上创建成对组合，提取元素并进行乘法

new_lst <- combn(seq_along(results), 2, \(i) matr[,i[1]] * matr[,i[2]] * 
    results[[i[1]]] * results[[i[2]]], simplify = FALSE)
names(new_lst) <- combn(seq_along(results), 2, paste, collapse="_")

-输出

> new_lst
$`1_2`
          [,1]      [,2]       [,3]
[1,] 64.135122 2.6966755 12.4307531
[2,]  2.696676 0.1133865  0.5226732
[3,] 12.430753 0.5226732  2.4093448

$`1_3`
          [,1]       [,2]      [,3]
[1,]  5.775451 -1.2624981 -5.095849
[2,] -1.262498  0.2759787  1.113939
[3,] -5.095849  1.1139391  4.496217

$`1_4`
          [,1]      [,2]       [,3]
[1,]  18.46710 -2.275650 -18.610758
[2,]  -2.27565  0.280422   2.293352
[3,] -18.61076  2.293352  18.755530

$`2_3`
          [,1]      [,2]      [,3]
[1,] 43.621251 -7.589849 -9.242303
[2,] -7.589849  1.320590  1.608108
[3,] -9.242303  1.608108  1.958223

$`2_4`
          [,1]       [,2]       [,3]
[1,] 139.47970 -13.680683 -33.754187
[2,] -13.68068   1.341852   3.310735
[3,] -33.75419   3.310735   8.168537

$`3_4`
          [,1]     [,2]      [,3]
[1,] 12.560327 6.404863 13.837154
[2,]  6.404863 3.266019  7.055953
[3,] 13.837154 7.055953 15.243778

R中列表对象之间的矩阵计算

Matrix calculation between list objects in R

r

list

matrix

apply

matrix-multiplication