Subsetting a list of lists using lapply

Hmm?Chuck?s solution may actually be problematic because there are several entries which at the deepest level are called ?sha?, but that should not be included, such as:

input[[67]]$content[[1]]$commit$tree$sh

and

input[[67]]$content[[1]]$parents[[1]]$sha

it?s only the ?sha? that fit the following subsetting pattern that should be included:

input[[i]]$content[[1]]$sha[1]

It?s getting thornier!

To be fair to Rolf?s solution (which probably can be updated to solve the problem), I?ve posted the complete dput here:

https://gist.githubusercontent.com/aronlindberg/92700c04c88ff112e4f7/raw/0f3cd8468f4dc82267be3cec72d53a7a04f5c449/dput.R
I didn't try on the larger example, but this works on the smaller one:

 get_shas <- function(input){
	x <- lapply(input, "[[", "content")
        y <- lapply(x, "[[", 1)   
	z <- lapply(y, function(yy) if( length(names(yy)) && names(yy) =="sha"  ){ yy[["sha"]] })
	}
      sha_lists <- get_shas(input)

It does deliver an entry for every leaf of the input-object which is either the value of "sha" or NA. I think that is not a bad thing because it lets you figure out where the values are coming from.
-- 

Aron Lindberg

Doctoral Candidate, Information Systems

Weatherhead School of Management 

Case Western Reserve University

aronlindberg.github.io

On Fri, Feb 20, 2015 at 8:25 AM, Aron Lindberg <aron.lindberg at case.edu>
wrote:

Thanks Chuck and Rolf.
While Rolf?s code also works on the dput that I actually gave you (a smaller subset of the full dataset), it failed to work on the larger dataset, because there are further exceptions:
input[[i]]$content[[1]] is sometimes a list, sometimes a character vector, and sometimes input[[i]]$content simply returns list().
Chuck?s solution however bypasses this and works on the full dataset (which was 8mb, which is why I didn?t upload it as a gist).
Best,
Aron
-- 
Aron Lindberg
Doctoral Candidate, Information Systems
Weatherhead School of Management 
Case Western Reserve University
aronlindberg.github.io
On Fri, Feb 20, 2015 at 12:44 AM, Charles Berry <ccberry at ucsd.edu> wrote:
Aron Lindberg <aron.lindberg <at> case.edu> writes:
Hi Everyone,

I'm working on a thorny subsetting problem involving list of lists. I've put a 
dput of the data here:
	https://gist.githubusercontent.com/aronlindberg/b916dee897d051ac5be5/
raw/a78cbf873a7e865c3173f943ff6309ea688c653b/dput

IIUC, you want the value of every list element that is named "sha" and 
that name will only apply to atomic objects.
If so, this should do it. 
input <- dget("/tmp/dpt")
shas <- unlist( input, use.names=FALSE )[ grepl( "sha", names(unlist(input)))]
input[[67]]$content[[1]]$sha
[1] "58cf43ecdc1beb7e1043e9de612ecc817b090f15"
which(input[[67]]$content[[1]]$sha == shas )
[1] 194
HTH,
Chuck
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David Winsemius
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Subsetting a list of lists using lapply

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