Am I missing something? Passing rev() to order() isn't going to do
anything, if I have enough coffee this morning. For numeric, one can pass
negatives to order(), but for character/factor, something else is needed, I
believe.
Andy
> From: Jean V Adams
>
> Isn't using rev() a more convenient approach?
>
> In your example:
> Oats[order(rev(Oats$nitro), Oats$Variety), ]
>
> For Thom Burnett's recently posted example:
> attach(unsortedData)
> sortedData <- unsortedData[order(sex, rev(race),
> rev(smoking), weight), ]
> detach("unsortedData")
>
> JVA
>
> `·.,, ><(((º> `·.,, ><(((º> `·.,, ><(((º>
>
> Jean V. Adams
> Statistician
> U.S. Geological Survey
> Great Lakes Science Center
> c/o Marquette Biological Station
> 1924 Industrial Parkway
> Marquette, MI 49855 USA
> phone: 906-226-1212
> FAX: 906-226-3632
> web site: www.glsc.usgs.gov
> e-mail: jvadams@usgs.gov
>
>
>
>
>
> Kevin Wright
>
>
> <kwright@eskimo.com> To:
> s-news@lists.biostat.wustl.edu
>
> Sent by: cc:
>
>
> s-news-owner@lists.biosta
> Subject: [S] General-purpose function for sorting data frame
>
> t.wustl.edu
>
>
>
>
>
>
>
>
> 09/29/2004 10:04 AM
>
>
>
>
>
>
>
>
>
>
> One of the often asked questions on s-news and r-help relates
> to sorting
> a data frame in ascending/descending order by multiple columns.
>
> I have created a function that does the job very flexibly and
> in a way that
> should be easy to remember. For example, to sort the Oats
> data.frame (nlme
> library) by nitro (decreasing) and Variety (increasing) :
>
> sort.data.frame(Oats, ~ -nitro + Variety)
>
> Feedback and improvements are welcome.
>
> sort.data.frame <- function(form,dat){ # Author: Kevin Wright
> # Some ideas from Andy Liaw
> # http://tolstoy.newcastle.edu.au/R/help/04/07/1076.html
>
> # Use + for ascending, - for decending.
> # Sorting is left to right in the formula
>
> # Useage is either of the following:
> # library(nlme); data(Oats)
> # sort.data.frame(~-Variety+Block,Oats) # Note: levels(Oats$Block)
> # sort.data.frame(Oats,~nitro-Variety)
>
> # If dat is the formula, then switch form and dat
> if(inherits(dat,"formula")){ f=dat
> dat=form
> form=f
> }
> if(form[[1]] != "~")
> stop("Formula must be one-sided.")
>
> # Make the formula into character and remove spaces
> formc <- as.character(form[2])
> formc <- gsub(" ","",formc)
> # If the first character is not + or -, add +
> if(!is.element(substring(formc,1,1),c("+","-")))
> formc <- paste("+",formc,sep="")
>
> # Extract the variables from the formula
> if(exists("is.R") && is.R()){ vars <- unlist(strsplit(formc,
> "[\\+\\-]"))
> }
> else{ vars <- unlist(lapply(unpaste(formc,"-"),unpaste,"+"))
> }
> vars <- vars[vars!=""] # Remove spurious "" terms
>
> # Build a list of arguments to pass to "order" function
> calllist <- list()
> pos=1 # Position of + or -
> for(i in 1:length(vars)){ varsign <- substring(formc,pos,pos)
> pos <- pos+1+nchar(vars[i])
> if(is.factor(dat[,vars[i]])){ if(varsign=="-")
> calllist[[i]] <- -rank(dat[,vars[i]])
> else
> calllist[[i]] <- rank(dat[,vars[i]])
> }
> else {
> if(varsign=="-")
> calllist[[i]] <- -dat[,vars[i]]
> else
> calllist[[i]] <- dat[,vars[i]]
> }
> }
> dat[do.call("order",calllist),]
>
> }
>
>
>
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