[R] cumsum vs. sum
maechler at stat.math.ethz.ch
Wed Feb 18 17:39:03 CET 2009
>>>>> "SM" == Stavros Macrakis <macrakis at alum.mit.edu>
>>>>> on Wed, 18 Feb 2009 10:00:40 -0500 writes:
SM> Nice! Glad to hear it. It sounds as though it is still possible for
SM> cumsum(x)[length(x)] to not be exactly equal to sum, though?
Well, possible, probably yes, platform-dependently;
However I vaguely remember that I didn't see one such case in the few
experiments I did.
SM> On Wed, Feb 18, 2009 at 8:03 AM, Martin Maechler
SM> <maechler at stat.math.ethz.ch> wrote:
>> o cumsum(x) and cumprod(x) for double precision x now use a long
>> double accumulator where available and so more closely match
>> sum() and prod() in potentially being more accurate.
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