使用 R、dplyr 矩阵的总和列表列（来自嵌套的 data.frame）

Question

I have a grouped data.frame , with a column m that contains 2x2 matrices, as in this example:

library(tidyverse)
d <- data.frame(g=c(1,1,2,2),x1=c(1,1,1,1),x2=c(1,1,1,1))
d_by <- d  %>%  group_by(g) %>% nest %>% 
  mutate(m = map(data,data.matrix))
d_by$m %>% str

How can I add the matrices in list-column m into a single matrix?

I tried using

d_by %>% summarise(sum(m))

But got the error message:

Error in sum(m) : invalid 'type' (list) of argument

Answer 1

You can use reduce for an arbitrary number of matrices

purrr::reduce(d_by$m, `+`)

Answer 2

Or in base R

Reduce(`+`, d_by$m)