R: name list element by variable [closed]

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Probably been asked before and I've seen some similar questions, but I would like to name my list elements according to the name of a variable varname in the statements

m=list(list(a=1,b=2),list(a=1,b=2))
v=1:length(m)
varname="c"
m=lapply(1:length(m), function(i) modifyList(m[[i]],list(varname=v[[i]])))

where m is a nested list and v a vector of the same length.

Problem is this returns me with sublists that are named varname as opposed to "c":

m
[[1]]
[[1]]$a
[1] 1

[[1]]$b
[1] 2

[[1]]$varname
[1] 1


[[2]]
[[2]]$a
[1] 1

[[2]]$b
[1] 2

[[2]]$varname
[1] 2

Probably quite trivial, but how should I solve this?

You should provide a reproducible example ! what is modifyList ? — agstudy
– agstudy, Commented Jun 24, 2014 at 12:11
No because that will rename the top level, whereas I want to rename sublist $varname to $c. Also I was just wondering if it could all be done in just one line, within the lapply statement. — Tom Wenseleers
– Tom Wenseleers, Commented Jun 24, 2014 at 12:19
Do you need to add variable c or rename existing (a,b) to c? — zx8754
– zx8754, Commented Jun 24, 2014 at 12:26

Ben Bolker · Accepted Answer · 2014-06-24 12:29:52Z

3

m=list(list(a=1,b=2),list(a=1,b=2))
v=1:length(m)
varname="c"

This will work:

m2=lapply(1:length(m), 
     function(i) modifyList(m[[i]],setNames(list(v[[i]]),varname)))

or

m2=mapply(function(x,y) {x[[varname]] <- y; x},m,v,SIMPLIFY=FALSE)

answered Jun 24, 2014 at 12:29

Ben Bolker

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1 Comment

Tom Wenseleers Over a year ago

Ha that's great - many thanks!! I finally hope to get my head around these kind of things :-)

amblina · Accepted Answer · 2014-06-24 12:49:42Z

1

I'm not able to comment on David Arenburg's comment above, however if you do this you can adjust it to have a vector of names.

m=list(list(a=1,b=2),list(a=1,b=2))
v=1:length(m)
varname=c('Var1','Var2')
names(m) <- rep(varname, length(m)/length(varname))

m now looks like this:

$Var1
$Var1$a
[1] 1

$Var1$b
[1] 2


$Var2
$Var2$a
[1] 1

$Var2$b
[1] 2

You can call the values in the list like you would a dataframe (with a $) like this:

m$Var1$a which will return 1

answered Jun 24, 2014 at 12:49

amblina

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