Hi R-devel,

Today I was needing a way to "merge" two different lists (see the example for my definition of merge). I didn't find anything relevant using different search methods.
So, here is my proposal to add a list method for "merge".


Best wishes,

Eric

PS: AFAIK, there still is no place for code snipplets. I am not sure this mail doesn't suite R-devel. If not, what place could there be for discussions/proposal on such code snipplets?

-- CODE

merge.list=function(x,y,only.new.y=FALSE,append=FALSE,...)
{
    out=x

     ystructure = names(c(y,recursive=TRUE))
     xstructure = names(c(x,recursive=TRUE))
     yunique = ystructure[! ystructure %in% xstructure]

ystructure = sapply(ystructure,FUN=function(element) strsplit(element,"\\."))
xstructure = sapply(xstructure,FUN=function(element) strsplit(element,"\\."))
yunique = sapply(yunique,FUN=function(element) strsplit(element,"\\."))


if (only.new.y) lapply(yunique, FUN=function(index) out[[index]]<<-y[[index]])
else
{
if (!append){
lapply(ystructure, FUN=function(index) out[[index]]<<-y[[index]])
}
else lapply(ystructure, FUN=function(index) out[[index]]<<-c(out[[index]],y[[index]]))
}
return(out)
}


-- SAMPLE
> (l1=list(a=list(a1=1,a2=2),b=list(b1=1)))
$a
$a$a1
[1] 1

$a$a2
[1] 2


$b $b$b1 [1] 1


> (l2=list(a=list(a1=-1,a3=3),c=pi)) $a $a$a1 [1] -1

$a$a3
[1] 3


$c [1] 3.141593

> merge(l1,l2)
$a
$a$a1
[1] -1

$a$a2
[1] 2

$a$a3
[1] 3


$b $b$b1 [1] 1


$c [1] 3.141593

> merge(l1,l2,append=TRUE)
$a
$a$a1
[1]  1 -1

$a$a2
[1] 2

$a$a3
[1] 3


$b $b$b1 [1] 1


$c [1] 3.141593

> merge(l1,l2,only.new.y=TRUE)
$a
$a$a1
[1] 1

$a$a2
[1] 2

$a$a3
[1] 3


$b $b$b1 [1] 1


$c [1] 3.141593

>

--
Eric Lecoutre
UCL /  Institut de Statistique
Voie du Roman Pays, 20
1348 Louvain-la-Neuve
Belgium

tel: (+32)(0)10473050
[EMAIL PROTECTED]
http://www.stat.ucl.ac.be/ISpersonnel/lecoutre

If the statistics are boring, then you've got the wrong numbers. -Edward Tufte

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