[R] removing NULL elements from a list

[Prof Brian Ripley]

On Mon, 14 Apr 2003, Vadim Ogranovich wrote:

> you can also modify the original list "in place":
> 
> l[sapply(l, is.null)] <- NULL
> 
> 
> I don't understand why it works this way especially given that, for example,
> 
> l[sapply(l, is.null)] <- 5
> 
> simply replaces NULL elements of the list with 5. This probably has to do
> with the special semantics of NULL. I'd appreciate if someone could clearify
> this for me.

It's in the FAQ.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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