On Fri, 1 Oct 2010, Dimitri Liakhovitski wrote:
> Hello!
>
> In the example below the Reduce() function by default assigns "a"
to
> be the last accumulated value and "b" to be the current value in
"x".
> I could not find this documented anywhere as the default settings for
> the Reduce() function. Does any sort of documentation for this
> behavior exist?
Yes.
Under 'Details' on the Reduce help page:
"... a left reduce computes l_1 = f(v_1, v_2), l_2 = f(l_1, v_3),
etc..."
HTH,
Chuck>
> x <- c(0,0,0,0,0,1,0,0,0,5,0,0,0,7,0,0,0,8,5,10)
> Reduce(function(a,b) b + (a * 0.5),x,accumulate=T,init=0)
>
> [1] 0.0000000 0.0000000 0.0000000 0.0000000 0.0000000 0.0000000
> 1.0000000 0.5000000 0.2500000
> [10] 0.1250000 5.0625000 2.5312500 1.2656250 0.6328125 7.3164062
> 3.6582031 1.8291016 0.9145508
> [19] 8.4572754 9.2286377 14.6143188
>
>
> Thanks a lot!
>
> --
> Dimitri Liakhovitski
> Ninah Consulting
> www.ninah.com
>
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>
Charles C. Berry (858) 534-2098
Dept of Family/Preventive Medicine
E mailto:cberry at tajo.ucsd.edu UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901