[R] Remove empty list from list - remove only one row and make as matrix

[Dimitris Rizopoulos]

try the following:

# a
dff[sapply(dff, is.matrix)]

# b
lapply(dff, function(x) if(!is.matrix(x)) rbind(x) else x)


I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Muhammad Subianto" <msubianto at gmail.com>
To: <r-help at stat.math.ethz.ch>
Sent: Tuesday, August 29, 2006 1:22 PM
Subject: Re: [R] Remove empty list from list - remove only one row and 
make as matrix


> Dear all,
> After I work around, I found in my list of data with only one row 
> which
> need to remove or make it as matrix.
> Here I write again my other toy example:
> x <- list(matrix(1:20, 5, 4),matrix(1:20, 5, 4),matrix(1:20, 5,
> 4),matrix(1:20, 5, 4),matrix(1:20, 5, 4))
> y <- list(c(1, -1, -1, 1, 1),c(1, -1, -1, -1, -1),c(1, 1, 1, 1, 
> 1),c(1,
> 1, -1, 1, -1),c(-1, -1, -1, -1, -1))
> ## Thanks to Gabor Grothendieck for this trick.
> ## SIMPLIFY? SIMPLIFY >< simplify
> xy.list <- mapply(cbind, x, y, SIMPLIFY=FALSE)
>
> point.class <-
> t(cbind(c(10,20,15,4,-1),c(21,10,15,34,-1),c(11,13,6,3,1),c(7,5,5,2,1),c(8,9,5,12,-1)))
> class.diffsame <- points.neighb(as.matrix(point.class), xy.list, 5)
> pd.class <- points.diff(class.diffsame,xy.list)
>
> nc.test <- vector("list",length(pd.class))
> for (i in 1:length(pd.class)) {
>      nc.test[[i]] <- pd.class[[i]]$point.diff
> }
> nc.test
>
> # delete null/empty entries in a list
> dff <- delete.NULLs(nc.test)
> dff; str(dff)
> > dff
> [[1]]
>      [,1] [,2] [,3] [,4] [,5]
> [1,]    1    6   11   16    1
> [2,]    4    9   14   19    1
> [3,]    5   10   15   20    1
>
> [[2]]
> [1]  1  6 11 16  1
>
> [[3]]
>      [,1] [,2] [,3] [,4] [,5]
> [1,]    3    8   13   18   -1
> [2,]    5   10   15   20   -1
>
> >
>
> lapply(dff, nrow)
> > lapply(dff, nrow)
> [[1]]
> [1] 3
>
> [[2]]
> NULL
>
> [[3]]
> [1] 2
>
> >
>
> #I can use
> #dff[unlist(lapply(dff, nrow) == 1)] #2,3, etc
>
> I have two questions here:
> a. I need to remove dff[[2]]
> b. How to make it as matrix (in list). I mean the result something 
> like
>
> [[1]]
>      [,1] [,2] [,3] [,4] [,5]
> [1,]    1    6   11   16    1
> [2,]    4    9   14   19    1
> [3,]    5   10   15   20    1
>
> [[2]]
>      [,1] [,2] [,3] [,4] [,5]
> [1]    1    6    11   16    1
>
> [[3]]
>      [,1] [,2] [,3] [,4] [,5]
> [1,]    3    8   13   18   -1
> [2,]    5   10   15   20   -1
>
>
> Best, Muhammad Subianto
>
>
> points.neighb <- function(p.class, list.nc, class.col) {
>    ntuples <- nrow(p.class)
>    instvec <- vector("list",length=ntuples)
>    for (i in 1:ntuples) {
>         # Thanks to Petr Pikal for this trick
>         instvec[[i]]$class.diff <- (p.class[i,class.col] -
> list.nc[[i]][,class.col])!=0
>         instvec[[i]]$class.same <- (p.class[i,class.col] -
> list.nc[[i]][,class.col])==0
>    }
>    instvec
> }
>
> points.diff <- function(p.class, list.nc) {
>    ntuples <- length(list.nc)
>    instvec <- vector("list",ntuples)
>    for (i in 1:ntuples) {
>         instvec[[i]]$point.diff <- 
> list.nc[[i]][p.class[[i]]$class.diff,]
>         instvec[[i]]$point.same <- 
> list.nc[[i]][p.class[[i]]$class.same,]
>    }
>    instvec
> }
>
> # Thanks to Jim Holtman for this trick
> delete.NULLs  <-  function(x.list){
>     x.list[unlist(lapply(x.list, length) != 0)]
> }
>
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