How to create a matrix from a list without a for loop

Dear R-Help-list,

   I have a list init_l containing 16 dataframes and I want to create a
matrix 4 x 4 from this list with a dataframe in every cell of the
matrix. I succeeded to do that but my loop is very uggly (cf. below).
Could somebody help me to write nice R code to do this loop ?

Thank you very much

Laurent


##
## mock data, 16 dataframes in a list
##
init_l <- lapply( seq(1,16) , function(x) {
   data.frame( V1 = rnorm(3),
               V2 = rnorm(3),
               V3 = rnorm(3)
             )
})

##
## lists matrix creation with n = 4 columns and n = 4 rows
##
n <- 4
## an example of row to create the matrix with lists in the cells
one_row <- rbind( rep( list(rep(list(1),3)) , n) )
mymat <- do.call( "rbind" , rep( list(one_row) , n) )

##
## The UGGLY loop I would like to improve:
##

## populate the matrix
k <- 1
for( i in 1:n){
   for( j in 1:n){
     mymat[i,j][[1]] <- list( init_l[[ k ]] )
     k <- k+1
   }
}

colnames(mymat) <- c("X1", "X2", "X3", "X3")
rownames(mymat) <- c("X1", "X2", "X3", "X4")


mymat

# X1     X2     X3     X3
# X1 List,1 List,1 List,1 List,1
# X2 List,1 List,1 List,1 List,1
# X3 List,1 List,1 List,1 List,1
# X4 List,1 List,1 List,1 List,1


#
# verification, it works
#
mymat[2,2]
init_l[[6]]

##
init_l[[6]]

library(tidyverse)
mymat.t <- as.tibble(mymat)
mymat.t
unnest(mymat.t[2,2],cols="X2")[[1]][[1]]

mymat.df <- as.data.frame(mymat)
mymat.df[2,2][[1]][[1]]


thx



--
L'absence de virus dans ce courrier ?lectronique a ?t? v?rifi?e par le
logiciel antivirus Avast.
https://www.avast.com/antivirus

Dear R-Help-list,

? I have a list init_l containing 16 dataframes and I want to create a 
matrix 4 x 4 from this list with a dataframe in every cell of the 
matrix. I succeeded to do that but my loop is very uggly (cf. below). 
Could somebody help me to write nice R code to do this loop ?

Thank you very much

Laurent


##
## mock data, 16 dataframes in a list
##
init_l <- lapply( seq(1,16) , function(x) {
? data.frame( V1 = rnorm(3),
????????????? V2 = rnorm(3),
????????????? V3 = rnorm(3)
??????????? )
})

##
## lists matrix creation with n = 4 columns and n = 4 rows
##
n <- 4

Try
? ?matrix(init_l, nrow=4, ncol=4, 
dimnames=list(c("X1","X2","X3","X4"),c("X1","X2","X3","X4")))
It doesn't give exactly what your code does, but your code introduces 
an extra level of "list", which you may not want.

-Bill

On Fri, Jul 9, 2021 at 10:40 AM Laurent Rhelp <LaurentRHelp at free.fr 
<mailto:LaurentRHelp at free.fr>> wrote:

    Dear R-Help-list,

    ?? I have a list init_l containing 16 dataframes and I want to
    create a
    matrix 4 x 4 from this list with a dataframe in every cell of the
    matrix. I succeeded to do that but my loop is very uggly (cf. below).
    Could somebody help me to write nice R code to do this loop ?

    Thank you very much

    Laurent


    ##
    ## mock data, 16 dataframes in a list
    ##
    init_l <- lapply( seq(1,16) , function(x) {
    ?? data.frame( V1 = rnorm(3),
    ?????????????? V2 = rnorm(3),
    ?????????????? V3 = rnorm(3)
    ???????????? )
    })

    ##
    ## lists matrix creation with n = 4 columns and n = 4 rows
    ##
    n <- 4
    ## an example of row to create the matrix with lists in the cells
    one_row <- rbind( rep( list(rep(list(1),3)) , n) )
    mymat <- do.call( "rbind" , rep( list(one_row) , n) )

    ##
    ## The UGGLY loop I would like to improve:
    ##

    ## populate the matrix
    k <- 1
    for( i in 1:n){
    ?? for( j in 1:n){
    ???? mymat[i,j][[1]] <- list( init_l[[ k ]] )
    ???? k <- k+1
    ?? }
    }

    colnames(mymat) <- c("X1", "X2", "X3", "X3")
    rownames(mymat) <- c("X1", "X2", "X3", "X4")


    mymat

    # X1???? X2???? X3???? X3
    # X1 List,1 List,1 List,1 List,1
    # X2 List,1 List,1 List,1 List,1
    # X3 List,1 List,1 List,1 List,1
    # X4 List,1 List,1 List,1 List,1


    #
    # verification, it works
    #
    mymat[2,2]
    init_l[[6]]

    ##
    init_l[[6]]

    library(tidyverse)
    mymat.t <- as.tibble(mymat)
    mymat.t
    unnest(mymat.t[2,2],cols="X2")[[1]][[1]]

    mymat.df <- as.data.frame(mymat)
    mymat.df[2,2][[1]][[1]]


    thx



    -- 
    L'absence de virus dans ce courrier ?lectronique a ?t? v?rifi?e
    par le logiciel antivirus Avast.
    https://www.avast.com/antivirus <https://www.avast.com/antivirus>

On 7/9/21 10:40 AM, Laurent Rhelp wrote:

Dear R-Help-list,

? I have a list init_l containing 16 dataframes and I want to create 
a matrix 4 x 4 from this list with a dataframe in every cell of the 
matrix. I succeeded to do that but my loop is very uggly (cf. below). 
Could somebody help me to write nice R code to do this loop ?

Thank you very much

Laurent


##
## mock data, 16 dataframes in a list
##
init_l <- lapply( seq(1,16) , function(x) {
? data.frame( V1 = rnorm(3),
????????????? V2 = rnorm(3),
????????????? V3 = rnorm(3)
??????????? )
})

##
## lists matrix creation with n = 4 columns and n = 4 rows
##
n <- 4

Just assign a dimension attribute and you will have your two 
dimensional structure

dim(init_l) <- c(n,n)
init_l[ 2,2]

[[1]]
????????? V1???????? V2???????? V3
1 -1.4103259? 1.9214184 -0.1590919
2? 0.1899490? 0.3842191? 2.4502078
3 -0.4282764 -0.9992190? 1.5384344

is.matrix(init_l)

[1] TRUE

Very effective solution, I hope I remember that for the nex time.

Thank you


Le 09/07/2021 ? 19:50, David Winsemius a ?crit?:

On 7/9/21 10:40 AM, Laurent Rhelp wrote:

Dear R-Help-list,

 ? I have a list init_l containing 16 dataframes and I want to create
a matrix 4 x 4 from this list with a dataframe in every cell of the
matrix. I succeeded to do that but my loop is very uggly (cf. below).
Could somebody help me to write nice R code to do this loop ?

Thank you very much

Laurent


##
## mock data, 16 dataframes in a list
##
init_l <- lapply( seq(1,16) , function(x) {
 ? data.frame( V1 = rnorm(3),
 ????????????? V2 = rnorm(3),
 ????????????? V3 = rnorm(3)
 ??????????? )
})

##
## lists matrix creation with n = 4 columns and n = 4 rows
##
n <- 4

Just assign a dimension attribute and you will have your two
dimensional structure

dim(init_l) <- c(n,n)
init_l[ 2,2]

[[1]]
 ????????? V1???????? V2???????? V3
1 -1.4103259? 1.9214184 -0.1590919
2? 0.1899490? 0.3842191? 2.4502078
3 -0.4282764 -0.9992190? 1.5384344

is.matrix(init_l)

[1] TRUE