Combine a List of Matrices to a Single Matrix by Rows

Combine a list of matrices to a single matrix by rows

Use do.call(rbind,...)

> m1 <- matrix(1, nrow=2, ncol=3)
> m2 <- matrix(2, nrow=3, ncol=3)
> l <- list(m1, m2)
> do.call(rbind, l)
     [,1] [,2] [,3]
[1,]    1    1    1
[2,]    1    1    1
[3,]    2    2    2
[4,]    2    2    2
[5,]    2    2    2

You may also be interested in the rbind.fill.matrix() function from the "plyr" package, which will also let you bind matrices with differing columns, filling in with NA where necessary.

> m1 <- matrix(1, nrow=2, ncol=3)
> m2 <- matrix(2, nrow=3, ncol=4)
> l <- list(m1, m2)
> library(plyr)
> rbind.fill.matrix(l)
     1 2 3  4
[1,] 1 1 1 NA
[2,] 1 1 1 NA
[3,] 2 2 2  2
[4,] 2 2 2  2
[5,] 2 2 2  2

How to combine matrices in lists of a list in R?

Use mapply with rbind like this:

do.call(mapply, c("rbind", mylist))

giving:

$A
     [,1] [,2]
[1,]    1    3
[2,]    2    4
[3,]    1    1
[4,]    2    1
[5,]    2    1

$B
     [,1] [,2] [,3]
[1,]    1    3    5
[2,]    2    4    6
[3,]    1    3    1
[4,]    2    2    1
[5,]    3    2    1

Bind vectors across lists to single list of matrices

One option is to transpose the list of lists, then reduce the list elements to a single dataset with cbind.fill, get the transpose (t) and assign the row names to NULL

library(tidyverse)
library(rowr)
list(list1, list2, list3) %>% 
    transpose %>% 
    map(~ reduce(.x, cbind.fill, fill = NA) %>% 
          t %>% 
         `row.names<-`(NULL))
#$a
#     [,1] [,2] [,3] [,4] [,5]
#[1,]    1    2    3    4    5
#[2,]    1    2    3    4   NA
#[3,]    1    2    3   NA   NA

#$b
#     [,1] [,2] [,3] [,4] [,5]
#[1,]    6    7    8    9   10
#[2,]    6    7    8    9   NA
#[3,]    6    7    8   NA   NA

#$c
#     [,1] [,2] [,3] [,4] [,5]
#[1,]   11   12   13   14   15
#[2,]   11   12   13   14   NA
#[3,]   11   12   13   NA   NA

---

Or using base R

do.call(Map, c(f = function(...) {l1 <- list(...)
   do.call(rbind, lapply(l1, `length<-`, max(lengths(l1))))},  
      mget(paste0("list", 1:3))))

Combine matrices with different arrays using loop FOR in R

Something like this?

src <- c(1, 2, 3, 4)
len <- length(src)
acc <- list()

for (i in 1:len) {
  c <- t(combn(src, i))
  zeros <- matrix(0, nrow = dim(c)[1], ncol = len - i)
  acc[[i]] <- cbind(c, zeros)
}

do.call(rbind, acc)

Output:

      [,1] [,2] [,3] [,4]
 [1,]    1    0    0    0
 [2,]    2    0    0    0
 [3,]    3    0    0    0
 [4,]    4    0    0    0
 [5,]    1    2    0    0
 [6,]    1    3    0    0
 [7,]    1    4    0    0
 [8,]    2    3    0    0
 [9,]    2    4    0    0
[10,]    3    4    0    0
[11,]    1    2    3    0
[12,]    1    2    4    0
[13,]    1    3    4    0
[14,]    2    3    4    0
[15,]    1    2    3    4

Explanation:

1. combn produces a matrix of combinations (albeit sideways from what you want, so transpose with t)
2. make a matrix of zeros with number of rows = number of combinations and number of columns = total length - length of combination on this iteration
3. bind column-wise
4. outside the loop, bind all the accumulated matrices for each iteration row-wise.

BTW, I looked the the combinations function you were using and I'm not sure if you need that over the built-in combn function which is why I used it. combn just gives you all combinations of a certain length, which is what you want.

Combine list of lists of matrices into a list of matrices

purrr::pmap iterates in parallel over list items and passes to the function you specify, so you can obtain your desired results with just

library(purrr)

temp %>% pmap(cbind)
## [[1]]
##      [,1] [,2] [,3] [,4]
## [1,]    1    3    3    3
## [2,]    1    3    3    3
## 
## [[2]]
##      [,1] [,2] [,3] [,4] [,5] [,6]
## [1,]    2    2    4    4    4    4
## [2,]    2    2    4    4    4    4

Combine matrices row by row

In the future, please include example data that is copy/pasteable, not just a picture.

m1 = matrix(1:6, ncol = 2)
m2 = matrix(7:12, ncol = 3)

combos = expand.grid(1:nrow(m1), 1:nrow(m2))
cbind(m1[combos$Var1, ], m2[combos$Var2, ])
#      [,1] [,2] [,3] [,4] [,5]
# [1,]    1    4    7    9   11
# [2,]    2    5    7    9   11
# [3,]    3    6    7    9   11
# [4,]    1    4    8   10   12
# [5,]    2    5    8   10   12
# [6,]    3    6    8   10   12

---

Related Topics