> None of this checks that runs of zero exist in a group; if they don't, you'll > get warnings > and -Inf in the output as max takes maxima of nothing. You can add extra > checks inside > the function if that bothers you.
Just adding a second argument, 0, to the call to max() will take care of that. Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On > Behalf > Of S Ellison > Sent: Thursday, October 31, 2013 11:27 AM > To: Carlos Nasher; r-help@r-project.org > Subject: Re: [R] Count number of consecutive zeros by group > > > If I apply your function to my test data: > > > .... > > the result is > > 1 2 3 > > 2 2 2 > > > ... > > I think f2 does not return the max of consecutive zeros, but the max of any > > consecutve number... Any idea how to fix this? > > The toy example of tapply using f2 does indeed return the maximum run lengths > irrespective of the value repeated. > If you want to select runs of a particular value, you can select according to > use $values > element of the rle object, again inside the function. > Modifying to accommodate that (and again avoiding a data frame name the same > as a > base R function name - you managed it again!): > > dfr <- data.frame(ID = c(1,1,1,2,2,3,3,3,3), x = c(1,0,0,0,0,1,1,0,1)) > > f3 <- function(x) { > runs <- rle(x == 0L) #Often wise to be careful with == and numbers ... see > FAQ 7.31 > with(runs, max(lengths[values])) > #This works because in this case the values in > #$values are TRUE for x==0 and FALSE otherwise; see ?'[' for why those > work > } > with(dfr, tapply(x, ID, f3)) > > or, more or less equivalently but a shade more generally > > f4 <- function(x, select=0L) { > runs <- rle(x ) > with(runs, max(lengths[values == select])) > } > with(dfr, tapply(x, ID, f4)) > > None of this checks that runs of zero exist in a group; if they don't, you'll > get warnings > and -Inf in the output as max takes maxima of nothing. You can add extra > checks inside > the function if that bothers you. > > > > > ******************************************************************* > This email and any attachments are confidential. Any use...{{dropped:8}} > > ______________________________________________ > 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. ______________________________________________ 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.
