From: Moshe Olshansky <m_olshansky_at_yahoo.com>

Date: Mon, 02 Jun 2008 19:09:45 -0700 (PDT)

R-help_at_r-project.org mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Tue 03 Jun 2008 - 02:12:20 GMT

Date: Mon, 02 Jun 2008 19:09:45 -0700 (PDT)

A simpler solution would be:

*> x <- c(3,2,0,1,0,2,0,0,1,0,0,0,0,4,1)
*

> y <- rep(NA,length(x))

*> y
*

[1] NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA

*> z <- which(x != 0)
**> l <- z - c(1,z[-length(z)])
*

> y[z] <- log(x[z]/(l+1))

*> y
*

[1] 1.0986123 0.0000000 NA -1.0986123 NA -0.4054651 NA NA -1.3862944 [10] NA NA NA NA -0.4054651 -0.6931472

- On Tue, 3/6/08, Marc Schwartz <marc_schwartz_at_comcast.net> wrote:

*> From: Marc Schwartz <marc_schwartz_at_comcast.net>
**> Subject: Re: [R] NOT-SO-SIMPLE function!
**> To: "T.D.Rudolph" <prairie.picker_at_gmail.com>
**> Cc: r-help_at_r-project.org
**> Received: Tuesday, 3 June, 2008, 5:59 AM
*

> on 06/02/2008 01:30 PM T.D.Rudolph wrote:

*> > I am trying to set up a function which processes my
**> data according to the
**> > following rules:
**> >
**> > 1. if (x[i]==0) NA
**> > 2. if (x[i]>0) log(x[i]/(number of consecutive
**> zeros immediately preceding
**> > it +1))
**> >
**> > The data this will apply to include a variety of whole
**> numbers not limited
**> > to 1 & 0, a number of which may appear
**> consecutively and not separated by
**> > zeros. Below is an example with a detailed
**> explanation of the output
**> > desired:
**> >
**> > x <- c(3,2,0,1,0,2,0,0,1,0,0,0,0,4,1)
**> > output desired = c(1.098, 0.69, NA, -0.69, NA, -0.41,
**> NA, NA, 1.098, NA, NA,
**> > NA, NA, -0.22, 0)
**> >
**> > the 1st element, 3, becomes log(3) = 1.098612
**> > the 2nd element, 2, becomes log(2) = 0.6931472
**> > the 3rd element, 0, becomes NA (cannot log zero).
**> > the 4rd element, 1, becomes log(1/(1(number of
**> consecutive zeros immediately
**> > preceding it) + 1 (constant))) = log(1/2) =
**> -0.6931472
**> > the 5th element, 0, becomes NA
**> > the 6th element, 2, becomes log(2/(1(number of
**> consecutive zeros immediately
**> > preceding it) + 1 (constant))) = log(2/3) = -0.4054651
**>
**>
**> The above should be log(2/2) = 0
**>
**> There is only 1 consecutive zero preceding the 2 in the 6th
**> position
**>
**> > the 7th and 8th elements, both zeros, become NA
**> > the 9th element, 1, becomes log(1/(2(number of
**> consecutive zeros immediately
**> > preceding it) + 1 (constant))) = log(1/3) = 1.098612
**>
**> The above should be log(1/3) = -1.098612 (negative, not
**> positive)
**>
**> > the 10-13th elements, all zeros, each become NA
**> > the 14th element, 4, becomes log(4/(4(number of
**> consecutive zeros
**> > immediately preceding it) + 1 (constant))) = log(4/5)
**> = -0.2231436
**> > the 15th element, 1, becomes log(1) = 0
**> >
**> > This one has been in the works for some time and I
**> can't quite seem to crack
**> > it.
**> > I would be indebted to anyone who could with success -
**> it seemed so simple
**> > at the offset!
**> > Tyler
**>
**> I am presuming that you have some typos/errors above in
**> your per element
**> explanation of the processing of the vector. If so, then
**> the following
**> should work as a first pass and could probably be optimized
**> further:
**>
**> zeroes <- function(x, i)
**> {
**> if (x[i] == 0) {
**> NA
**> } else if (i == 1) {
**> log(x[i])
**> } else if (x[i - 1] != 0) {
**> log(x[i])
**> } else {
**> rz <- rle(x[1:(i-1)])
**> log(x[i] / (rz$lengths[length(rz$lengths)] + 1))
**> }
**> }
**>
**>
**> x <- c(3, 2, 0, 1, 0, 2, 0, 0, 1, 0, 0, 0, 0, 4, 1)
**>
**>
**> > sapply(seq(along = x), function(i) zeroes(x, i))
**> [1] 1.0986123 0.6931472 NA -0.6931472
**> NA 0.0000000
**> [7] NA NA -1.0986123 NA
**> NA NA
**> [13] NA -0.2231436 0.0000000
**>
**>
**> See ?rle for more information on the identification of the
**> sequential
**> zeroes in the vector.
**>
**> HTH,
**>
**> Marc Schwartz
**>
**> ______________________________________________
**> R-help_at_r-project.org mailing list
**> https://stat.ethz.ch/mailman/listinfo/r-help
**> PLEASE do read the posting guide
**> http://www.R-project.org/posting-guide.html
**> and provide commented, minimal, self-contained,
**> reproducible code.
*

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