l2array: Convert list of arrays to array

Description

Convert a list of arrays to a single array, conserving names. If dimnames do not need to be checked, you can also directly use
do.call(abind::abind, list(LIST, rev.along=0, use.dnns=TRUE))

Usage

l2array(x, ...)

Value

array

Arguments

x: List with arrays/data.frames. The dimension of the first is target dimension.
...: Further arguments passed to abind::abind

Author

Berry Boessenkool, berry-b@gmx.de, Dec 2016

Examples

Run this code


LISTm <- lapply(list(1:6,7:12,13:18,19:24), matrix, ncol=3,
               dimnames=list(x=c("a","b"), y=c("i","j","k"))  )
l2array(LISTm)

LIST <- lapply(LETTERS[1:5], function(x) array(paste0(x,1:24), dim=c(3,4,2)))
str(LIST)
LIST[[2]]
LISTa1 <- l2array(LIST)
LISTa1
str(LISTa1)

# The old l2array (<1.13.14, 2017-01-06) was very slow on large lists.
# I then found abind, which is much much much faster and easier on memory!
# It now replaces the internal old actual conversion code
# l2array still checks the dimnames
LISTa2 <- do.call(abind::abind, list(LIST, rev.along=0, use.dnns=TRUE))
LISTa2
stopifnot(all(LISTa1==LISTa2))
rm(LIST, LISTa1, LISTa2)


# list of dataframes:
LDF <- list(IR1=iris[1:5,1:2], IR2=iris[11:15,1:2], IR3=iris[21:25,1:2])
l2array(LDF)



# General intro to arrays -----

A1 <- array(1:24, dim=c(4,2,3), dimnames=list(
                   my_x=paste0("row",1:4), my_y=c("A","B"), paste0("n",1:3)))
A1
which(A1==20, arr.ind=TRUE)

# Selection:
A1[,,"n2"]
A1[,,1:2]
A1["row2",,] # result rotated against expectation -> transpose with t(...)
A1[,"A",]
# aggregation:
apply(A1, MARGIN=1:2, FUN=sum) # keep first two dimensions
apply(A1, MARGIN=c(1,3), FUN=sum) # aggregate over my_y -> row1: 6, 22, 38
A1["row1",,]                                    # 1+5=6, 9+13=22, 17+21=38

as.vector(A1)

A <- array(1:24, dim=c(3,4,2), dimnames=list(x=paste0("x",1:3),
                                             y=paste0("y",1:4),
                                             z=paste0("z",1:2)))
str(A)
rm(A)


# l2array -----

A2 <- A1+2
A3 <- A1+4
LIST <- list(A1=A1, A2=A2, A3=A3) # list of arrays

LA <- l2array(LIST)
LA
str(LA)
LA[,,,"A2"]
LA["row2", ,"n2",]
avg <- apply(LA, MARGIN=1:3, mean)
stopifnot(all(avg==A2))


# names check -----

LISTN <- LIST
names(dimnames(LISTN[[2]]))[3] <- "intentional"
dimnames(LISTN[[3]])[3] <- list(paste0("k",1:3))
LAN <- l2array(LISTN)
LAN["row2", ,"k2",] # n2 is now changed to k2
LANa <- do.call(abind::abind, list(LISTN, rev.along=0, use.dnns=TRUE))
all(LAN==LANa)
str(LANa)

LISTN <- LIST
rownames(LISTN[[3]])[2] <- "intentional_diff"
LAN <- l2array(LISTN)

# data type check
is.error(   A <- l2array(c(LA, 999)),  tell=TRUE, force=TRUE)