R transform a list of vectors with differing lengths into a matrix-CodePudding

I have the following list that I would like to transform into the matrix M:

L<-list(c(2L, 29L, 30L), c(1L, 3L, 30L, 31L), c(2L, 31L, 32L), c(5L, 
60L), c(4L, 6L, 60L, 61L), c(5L, 7L, 61L, 62L))

[[1]]
[1]  2 29 30

[[2]]
[1]  1  3 30 31

[[3]]
[1]  2 31 32

[[4]]
[1]  5 60

[[5]]
[1]  4  6 60 61

[[6]]
[1]  5  7 61 62

Matrix M:

2 29 30 NA
1 3 30 31
2 31 32 NA
5 60 NA NA
4 6 60 61
5 7 61 62

I want each list to be a row of the matrix and to fill in any missing values with NA.

CodePudding user response：

Append NA at the end of each list element based on the max length of the list element with length<- and then use rbind with do.call

mx <- max(lengths(L))
do.call(rbind, lapply(L, `length<-`, mx))

-output

    [,1] [,2] [,3] [,4]
[1,]    2   29   30   NA
[2,]    1    3   30   31
[3,]    2   31   32   NA
[4,]    5   60   NA   NA
[5,]    4    6   60   61
[6,]    5    7   61   62

CodePudding user response：

You could also use stri_list2matrix function from stringi package. This converts the vectors of list to character matrix so you should convert it to numeric if necessary like this:

L<-list(c(2L, 29L, 30L), c(1L, 3L, 30L, 31L), c(2L, 31L, 32L), c(5L, 
                                                                 60L), c(4L, 6L, 60L, 61L), c(5L, 7L, 61L, 62L))


library(stringi)
m <- stri_list2matrix(L, byrow=TRUE)
class(m) <- "numeric"
m
#>      [,1] [,2] [,3] [,4]
#> [1,]    2   29   30   NA
#> [2,]    1    3   30   31
#> [3,]    2   31   32   NA
#> [4,]    5   60   NA   NA
#> [5,]    4    6   60   61
#> [6,]    5    7   61   62

^{Created on 2022-07-29 by the reprex package (v2.0.1)}

CodePudding user response：

There would be better ways, but this works:

L<-list(c(2L, 29L, 30L), c(1L, 3L, 30L, 31L), c(2L, 31L, 32L), c(5L, 
60L), c(4L, 6L, 60L, 61L), c(5L, 7L, 61L, 62L))

out <- matrix(nrow=6, ncol=4)
for(i in 1:length(L)) {
  out[i, ] <- c(L[[i]], rep(NA, (4-length(L[[i]]))))
}

out

#      [,1] [,2] [,3] [,4]
# [1,]    2   29   30   NA
# [2,]    1    3   30   31
# [3,]    2   31   32   NA
# [4,]    5   60   NA   NA
# [5,]    4    6   60   61
# [6,]    5    7   61   62

CodePudding user response：

Another possible solution, based on purrr::map_dfr:

library(tidyverse)

map_dfr(L, ~ .x %>% set_names(LETTERS[1:length(.x)])) %>% 
  as.matrix %>% unname

#>      [,1] [,2] [,3] [,4]
#> [1,]    2   29   30   NA
#> [2,]    1    3   30   31
#> [3,]    2   31   32   NA
#> [4,]    5   60   NA   NA
#> [5,]    4    6   60   61
#> [6,]    5    7   61   62

And more simply:

tibble(L) %>% unnest_wider(L) %>% suppressMessages %>% as.matrix %>% unname