[R] extract from a list of lists

Greg Snow 538280 @end|ng |rom gm@||@com
Tue Dec 27 18:45:31 CET 2022

Another option is the map family of functions in the purrr package
(yes, this depends on another package being loaded, which may affect
things if you are including this in your own package, creating a

In map and friends, if the "function" is a string or integer, then it
is taken as the piece to be extracted, so you should be able to do
something like:

map(fits, 'iter')
# or
map_int(fits, 'iter')
# or
map_dbl(fits, 'iter')

which of the last 2 to use depends on how `iter` is stored.

On Tue, Dec 27, 2022 at 10:16 AM Therneau, Terry M., Ph.D. via R-help
<r-help using r-project.org> wrote:
> I not uncommonly have the following paradym
>     fits <- lapply(argument, function)
> resulting in a list of function results.   Often, the outer call is to mclapply, and the
> function encodes some long calculation, e.g. multiple chains in an MCMC.
> Assume for illustration that each function returns a list with elements   beta, loglik,  iter.
> Then  sapply(fits,  function(x) x$iter)
> will give me a vector, with the number of iterations used by each instance.
> I've often been suspicious that there is some simple shorthand for the "grab all the
> elements named iter" that skips the explicit x$iter function.   Am I indeed overlooking
> something?    I don't expect a speed increase, just cleaner code.
> Terry T.
> --
> Terry M Therneau, PhD
> Department of Quantitative Health Sciences
> Mayo Clinic
> therneau using mayo.edu
> "TERR-ree THUR-noh"
>         [[alternative HTML version deleted]]
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Gregory (Greg) L. Snow Ph.D.
538280 using gmail.com

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