[R] Generalized cumsum?
OKB (not okblacke)
brenbarn at brenbarn.net
Wed Sep 16 23:00:41 CEST 2009
Is there anything like cumsum and cumprod but which allows you to
apply an arbitrary function instead of sum and product? In other words,
I want a function cumfunc(x, f) that returns a vector, so that for all n
up to the length of x
cumapply(x,f)[n] = f(x[1:n])
This would give cumsum and cumprod as special cases when f=sum or
f=prod.
I could write such a function, but I can't see a way to do it
without a loop, so I'm wondering if such a function exists that may be
speedier.
Thanks,
--
--OKB (not okblacke)
Brendan Barnwell
"Do not follow where the path may lead. Go, instead, where there is
no path, and leave a trail."
--author unknown
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