Greg, Thanks for the great explanation. Knowing the philosophy behind these kind of things really helps avoid problems in the future.
Aloha, Tim Tim Clark Department of Zoology University of Hawaii --- On Thu, 5/6/10, Greg Snow <greg.s...@imail.org> wrote: > From: Greg Snow <greg.s...@imail.org> > Subject: RE: [R] bar order using lattice barchart() > To: "Tim Clark" <mudiver1...@yahoo.com>, "r-help@r-project.org" > <r-help@r-project.org> > Date: Thursday, May 6, 2010, 7:51 AM > The short answer to your query is > ?reorder > > The longer answer (or a longer answer) gets into a bit of > philosophy (so feel free to go back to the short answer and > skip this if you don't want to get into the philosophy, you > have been warned). Let's start with the question: is > the order of the bars a property of the graph/analysis? The > dataset as a whole? Or the individual variable? > > Some programs take the first approach, the order is a > property of the graph or analysis, these programs have you > specify things like the order at the time of creating the > graph or doing the analysis. I don't like this > approach because it seems to me that this should be more > inherent to the data than the output, also this means that > you have to keep specifying the order for every > graph/analysis and I am too lazy to like that. > > Your attempt was number 2, the order should be a property > of the dataset. For your example this makes a lot of > sense, you want x ordered by y. But this does not > generalize to some other situations, so is not the standard > for R. > > My favorite (and what is used in R, so apparently I'm not > the only one) is to have things like the order be a property > of the individual variable (x in this case). Your data > frame will have x as a factor by default (and even if you > specifically told R to not convert it to a factor, then many > plotting/analysis functions will still convert it to a > factor). If you don't specify the order of the factor > levels then the default is to do it alphabetically and this > will be used by plotting/analysis functions regardless of > the order in the data set. One of the easier ways to > change the order of the factor levels, especially for a case > like yours is using the reoder function, try something > like: > > > xy$x <- reorder( xy$x, xy$y ) > > You won't see any obvious differences when you print the > data frame, but if you print just x then you should and your > plots should come out the way that you want now. > > You did ask "why?" and were warned. Hope this helps, > > -- > Gregory (Greg) L. Snow Ph.D. > Statistical Data Center > Intermountain Healthcare > greg.s...@imail.org > 801.408.8111 > > > > -----Original Message----- > > From: r-help-boun...@r-project.org > [mailto:r-help-boun...@r- > > project.org] On Behalf Of Tim Clark > > Sent: Wednesday, May 05, 2010 8:57 PM > > To: r-help@r-project.org > > Subject: [R] bar order using lattice barchart() > > > > Dear List, > > > > I am want to plot my data in increasing order using > the lattice > > barchart() function. I used order() to put my > data in the order I > > want, but when I plot it I get the original order of > the data. I think > > this has to do with the row index number since order() > does not re- > > number the rows in the new order but instead keeps the > original row > > numbers and puts them in a different order. For > example: > > > > xy<-data.frame(x=letters[1:5],y=c(3,9,2,1,10)) > > > > #This produces a dataframe in alphebitical order with > row numbers in > > #numerical order. > > > xy > > x > y > > 1 a 8.921657 > > 2 b 10.314625 > > 3 c 9.531537 > > 4 d 10.818563 > > 5 e 9.084872 > > > > > > #If I re-order the data based on the value of y > > > > xy<-xy[order(y),] > > > > #I get a dataframe ordered by y but the row numbers > are still in > > #alphebetical order based on x > > > xy > > x > y > > 1 a 8.921657 > > 5 e 9.084872 > > 3 c 9.531537 > > 2 b 10.314625 > > 4 d 10.818563 > > > > #I then try to plot the data and it plots it in > alphabetical instead of > > #numeric order > > library(lattice) > > barchart(y~x, data=xy) > > > > > > > > Why are the rows not re-indexed, and how do I get > barchart() to plot my > > data in increasing numeric order? > > > > Thanks, > > > > Tim > > > > > > > > > > Tim Clark > > Department of Zoology > > University of Hawaii > > > > ______________________________________________ > > 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.
