Consider the two level list created by following code:
a = list()
s = seq(1,5)
for (i in s) {
a[[i]] = list(field1 = i, field2 = letters[i])
}
Say I want to add a third element, "field3" to each sub-list, and do it with following combination of sapply(..) and the parent assignment operator:
sapply(s, function(x) a[[x]]$field3 <<- 5 - x)
Is this dangerous or considered abuse of the parent assignment operator? What is the recommended alternative? Are there potential speed gains from using this sapply statement instead of a for-loop?
I tend to use for-loop
s in this context. It's clearer and sapply
does not speed it up AFAIK, since sapply
is just a special case of a for-loop
under the hood. See here for details.
eg:
for (i in s) a[[i]]$field3 <- 5 - i
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