On Wed, 26 Aug 2009, Alistair Gee wrote:
If x is a vector (or data frame) that is in a particular order, and I
call split(x, f) to partition x, will the elements of each partition
remain in order?
They must for example( split ) to work as advertised, viz.
### Calculate z-scores by group
z <- unsplit(lapply(split(x, g), scale), g)
HTH,
Chuck
That is, is the following assertion always TRUE?
for(i in split(x, f)) {
stopifnot(!is.unsorted(i))
}
I suspect that this is the case, but the help page does not discuss
preservation of order in the result of split().
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Charles C. Berry (858) 534-2098
Dept of Family/Preventive Medicine
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