[R] removing NULL elements from a list

[Vadim Ogranovich]

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.

Thanks,
Vadim




> -----Original Message-----
> From: Peter Dalgaard BSA [mailto:p.dalgaard at biostat.ku.dk]
> Sent: Monday, April 14, 2003 10:07 AM
> To: Peter Dalgaard BSA
> Cc: R-Help (E-mail); Ramon Diaz
> Subject: Re: [R] removing NULL elements from a list
> 
> 
> Peter Dalgaard BSA <p.dalgaard at biostat.ku.dk> writes:
> 
> > l <- l[!lapply(l,is.null)]
> 
> ... sapply, of course, as Brian and Uwe said.
> 
> -- 
>    O__  ---- Peter Dalgaard             Blegdamsvej 3  
>   c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
>  (*) \(*) -- University of Copenhagen   Denmark      Ph: 
> (+45) 35327918
> ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: 
> (+45) 35327907
> 
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> 

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