[R] creating a list of lists from a data frame

From: Srinivas Iyyer <srini_iyyer_bio_at_yahoo.com>
Date: Thu, 27 Mar 2008 15:48:34 -0700 (PDT)


Dear group,
I have a dataframe (x). (4 rows, 3 columns for example)

I want to create a master list (my_list) from data frame.

I want each row of x to be a list.

I tried 3 different ways: writing a loop, using apply, and going through each row.
Going through each row works for me. since I have 1000 rows, I cannot manually create 1000 lists and combine them. I apologize for the long email with all 3 methods I tried. I request you to help me if I can automate last method. thanks srini

proposal:
x <- data frame

list1 <- list(src=x[1,]$V1,

              title = x[1,]$V2,
              pbset = X[1]$V3)
list2 <- list(src=x[2,]$V1,
              title = x[2,]$V2,
              pbset = X[2]$V3)

master_list <- list(list1,list2)

Solution:
Write a for loop that takes each row and creates a list.
Append this list to a master list.

Example:

> x

    title        src                  probesets
1  chr16q positional CMAR,USP10,PSORS8,WT3,SLI1
2   chr4p positional           ATP5I,MHW1,STGD4
3 chr1q13 positional                    SCARNA2
4  chr4q1 positional                   MORF4LP4

> mastr_list = list()

> for(i in 1:nrow(x)){

     y=list(src=as.character(x[i,src),
     title=as.character(x[i,]$title),
     probes=as.character(x[i,]$probesets))
      mastr_list[i]=y

    }

problem:
Warning messages:
1: In test[i] = y :
  number of items to replace is not a multiple of replacement length
2: In test[i] = y :
  number of items to replace is not a multiple of replacement length
3: In test[i] = y :
  number of items to replace is not a multiple of replacement length
4: In test[i] = y :
  number of items to replace is not a multiple of replacement length

> mastr_list
[[1]]
[1] "positional"

[[2]]
[1] "positional"

[[3]]
[1] "positional"

[[4]]
[1] "positional"

How can I make my master list.

I tried also apply function and result is not exactly what I desire.
>master_list <- apply(x, 1, list)
> master_list
[[1]]
[[1]][[1]]

                       title                         
src                    probesets 
                    "chr16q"                
"positional" "CMAR,USP10,PSORS8,WT3,SLI1"

[[2]]
[[2]][[1]]

             title                src         
probesets 
           "chr4p"       "positional"

"ATP5I,MHW1,STGD4"
[[3]]
[[3]][[1]]

       title src probesets
   "chr1q13" "positional" "SCARNA2"

[[4]]
[[4]][[1]]

       title src probesets
    "chr4q1" "positional" "MORF4LP4"

my final result should look like this:
> a =
list(src=as.character(x[1,]$src),title=as.character(x[1,]$title),probes=as.character(x[1,]$probesets)) > b =
list(src=as.character(x[2,]$src),title=as.character(x[2,]$title),probes=as.character(x[2,]$probesets)) > c =
list(src=as.character(x[3,]$src),title=as.character(x[3,]$title),probes=as.character(x[3,]$probesets)) > d =
list(src=as.character(x[4,]$src),title=as.character(x[4,]$title),probes=as.character(x[4,]$probesets)) > master_list = list(a,b,c,d)
> master_list
[[1]]
[[1]]$src
[1] "positional"

[[1]]$title
[1] "chr16q"

[[1]]$probes
[1] "CMAR,USP10,PSORS8,WT3,SLI1"

[[2]]
[[2]]$src
[1] "positional"

[[2]]$title
[1] "chr4p"

[[2]]$probes
[1] "ATP5I,MHW1,STGD4"

[[3]]
[[3]]$src
[1] "positional"

[[3]]$title
[1] "chr1q13"

[[3]]$probes
[1] "SCARNA2"

[[4]]
[[4]]$src
[1] "positional"

[[4]]$title
[1] "chr4q1"

[[4]]$probes
[1] "MORF4LP4"



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