In fact x[4,2] should = log(x[5,1]/2] whereas x[3,2] = log(x[5,1/3]) i.e. The denominator in the log function equals the number of rows between m==0 and m>0 (inclusive, hence the "+1")
Hope this helps!... Charles C. Berry wrote: > > On Tue, 27 May 2008, T.D.Rudolph wrote: > >> >> >> I have a matrix of frequency counts from 0-160. >> x<-as.matrix(c(0,1,0,0,1,0,0,0,1,0,0,0,0,1)) >> >> I would like to apply a function creating a new column (x[,2])containing >> values equal to: >> a) log(x[m,1]) if x[m,1] > 0; and >> b) for all x[m,1]= 0, log(next x[m,1] > 0 / count of preceding zero >> values >> +1) >> >> for example, x[1,2] should equal log(x[2,1]/2) = log(1/2) = -0.6931472 >> whereas x[3,2] should equal log(x[5,1]/3) = log (1/3) = -1.098612 >> > > If you also intend that x[4,2] == x[3,2] in your example, then this seems > what you want: > >> rle.x <- rle(x[,1]) >> num <- ifelse(rle.x$values == 0, c(tail(rle.x$values,-1),NA), >> rle.x$values ) >> denom <- ifelse(rle.x$values == 0 , rle.x$lengths +1 , 1 ) >> rep(log(num/denom),rle.x$lengths) > [1] -0.6931472 0.0000000 -1.0986123 -1.0986123 0.0000000 -1.3862944 > -1.3862944 -1.3862944 0.0000000 -1.6094379 > [11] -1.6094379 -1.6094379 -1.6094379 0.0000000 >> > > See > > ?rep > ?rle > ?tail > > HTH, > > Chuck > > >> I will be applying this to nrow(x)=~70,000 so I would prefer to not do it >> by >> hand! >> Tyler >> >> >> >> -- >> View this message in context: >> http://www.nabble.com/help-with-simple-function-tp17498394p17498394.html >> Sent from the R help mailing list archive at Nabble.com. >> >> ______________________________________________ >> R-help@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. >> > > Charles C. Berry (858) 534-2098 > Dept of Family/Preventive > Medicine > E mailto:[EMAIL PROTECTED] UC San Diego > http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901 > > ______________________________________________ > R-help@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. > > -- View this message in context: http://www.nabble.com/help-with-simple-function-tp17498394p17502735.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@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.
