Andy and Doug are right ... using rev() doesn't do what I said it would in
order().
Sorry 'bout that.
For numerics, you can use a negative sign to get descending order.
For factors, you can use a negative sign with as.numeric().
For characters, you can use a negative sign with as.numeric(as.factor()).
Or you can use Kevin's function.
JVA
"Jean V Adams"
<jvadams@usgs.gov> To:
kwright@eskimo.com
Sent by: cc:
s-news@lists.biostat.wustl.edu, Thom.Burnett@cognigencorp.com
s-news-owner@lists.biosta Subject: Re: [S]
General-purpose function for sorting data frame
t.wustl.edu
09/29/2004 10:35 AM
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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