[R] lapply / mapply and assignments

Magnus Torfason zulutime.net at gmail.com
Mon Oct 12 23:25:44 CEST 2009

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?


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