[R] Unlisting while preserving object types?

[Turner, Jason]

Hi

A toy example is probably the least ambiguous way of explaining what I'm
trying to do.

> library(ts)
> zz<-list(a=rnorm(100),b=rt(100,3))
> zz.spec<-lapply(zz,spectrum,plot=F)
> summary(zz.spec)
  Length Class Mode
a 15     spec  list
b 15     spec  list

I'm looking for an elegant way to fetch components of the sub-lists a and b
of zz.spec; 
e.g. to make a matrix with columns a$spec and b$spec.  

matrix(unlist(lapply(zz.spec,function(x){return(x$spec)})),ncol=length(zz.sp
ec))

is about the best I've come up with.  Is there a more direct way?  This gets
particularly
important with nested sub-lists - lists of lists of lists.  Is the best
approach is to 
have the good sense to avoid such structures in the first place?

Cheers

Jason

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