[R] lapply / mapply and assignments

[Charles C. Berry]

On Mon, 12 Oct 2009, Magnus Torfason wrote:

> I have a list of isometric structures, and I want to change the same part of 
> each structure in the list, assigning one element of a vector to each of 
> these parts.
>
> In other words, I want to achieve the following:
>
>>  l <- list( list(a=1,b=2), list(a=3,b=4))
>>  unlist(lapply(l, "[[", "a"))
> [1] 1 3
>>
>>  # This will not actually work
>>  l[[]]["a"] <- 5:6
>>
>>  unlist(lapply(l, "[[", "a"))
> [1] 5 6
>
> I figure mapply is the solution to the problem, and I tried the following:
>
>>  mapply( "[<-", l, "a", 5:6)
>
> But the result is not the same shape as the original.
>
> Any thoughts?

See

 	?relist

something like:

 	relist( unlist( mapply( "[<-", l, "a", 5:6) ), l )


HTH,

Chuck

>
> Best,
> Magnus
>
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Charles C. Berry                            (858) 534-2098
                                             Dept of Family/Preventive Medicine
E mailto:cberry at tajo.ucsd.edu	            UC San Diego
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