From: Gabor Grothendieck <ggrothendieck_at_myway.com>

Date: Mon 28 Mar 2005 - 03:46:23 EST

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Mon Mar 28 03:53:37 2005

Date: Mon 28 Mar 2005 - 03:46:23 EST

Seung Jun <jun <at> cc.gatech.edu> writes:

*:
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: Fold in Mathematica (or reduce in Python) works as follows:

*:
**: Fold[f, x, {a, b, c}] := f[f[f[x,a],b],c]
**:
**: That is, f is a binary operator, x is the initial value, and the results
**: are cascaded along the list. I've found it useful for reducing lists
**: when I only have a function that accepts two arguments (e.g., merge in R).
**:
**: Is there any R equivalent? I'm a newbie in R and having a hard time
**: finding such one. Thank you.
**:
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You could define it yourself like this:

Fold <- function(f, x, L) for(e in L) x <- f(x, e)

# example of its use

result <- Fold(sum, 0, 1:3) # result is 6

Note that merge.zoo in the zoo package does handle multiple arguments; however, that is intended for merging time series along their times, in case that is your application.

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Mon Mar 28 03:53:37 2005

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