[Rd] Potential improvements of ave? (Act 2)

SOEIRO Thomas Thom@@@SOEIRO @end|ng |rom @p-hm@|r
Sat Apr 17 21:24:06 CEST 2021

Dear list, 
This is a follow-up with another potential improvements of ave.
In the doc, x is documented as to be "a numeric", but this is not mandatory. 
DF <- data.frame(x = letters, group = rep(1:2, each = 13)) 
ave(DF$x, DF$group, FUN = function(i) "a") 
#  [1] "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" "a" 
# [20] "a" "a" "a" "a" "a" "a" "a" 
However coercion can raise issues if the type of x and FUN(x) do not match. Coercion happens in split<-.default in the for loop with x[i] <- value[[j]].
(NB: In the following example, we can work around the problem by wrapping x with as.numeric.)
DF <- data.frame(x = Sys.Date() + 1:10, group = rep(1:2, each = 5)) 
ave(DF$x, DF$group, FUN = function(i) 1) 
# Error in as.Date.numeric(value) : 'origin' must be supplied 
So I have 2 questions/suggestions: 
- Could the doc rather state that x must match the type of FUN(x) and warn for coercion?
- Could ave be more flexible (i.e. allow different type of x and FUN(x)) if using another approach than x[i] <- value[[j]] in split<-.default for recycling? 
This has already been discussed on r-help and stackoverflow (e.g. https://stat.ethz.ch/pipermail/r-help/2016-November/442855.html) 

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