Dear list, I´m having a little trouble with adding vertical lines to a histogram. I need to draw a matrix of histograms (using facets), and in each histogram add a vertical line indicating the mean value of the data in each facet. According to the last example in the geom_hline help, to display different lines in each facet I need to provide a data frame. I modified this example to make a plot similar to what I need:
# BEGIN R CODE ############################################ # This example works and does exactly what I need library(reshape) library(ggplot2) # First, create a data frame with the mean value, to add to each facet mean.data=tapply(mtcars$wt,INDEX=list(mtcars$vs,mtcars$am),mean) mean.data=melt(mean.data) colnames(mean.data)=c("vs","am","wt.mean") # Now do the plot p <- qplot(wt, data=mtcars) p <- p + facet_grid(vs ~ am,scale="free") p <- p + geom_vline(aes(xintercept = wt.mean), mean.data,col="red") p ########################################################### ########################################################### # This one does not work # Create a test data set set.seed(100) my.data=data.frame(code1=rep(c("A","B","C"),each=30), code2=rep(rep(c("D","E","F"),each=10),3), n=runif(90)) # Create a data frame with the mean value, to add to each facet mean.data=tapply(my.data$n,INDEX=list(my.data$code1,my.data$code2),mean) mean.data=melt(mean.data) colnames(mean.data)=c("code1","code2","n.mean") # Now do the plot p = qplot(n, data=my.data) + facet_grid(code2 ~ code1, scales="free") p + geom_vline(aes(xintercept = n.mean), mean.data,col="red") #With this I get the following error: "Error in if (length(range) == 1 || diff(range) == 0) { : missing value where TRUE/FALSE needed". # If I remove the "scales=free" argument. I get the lines but also a lot of extra empty facets. p = qplot(n, data=my.data) + facet_grid(code2 ~ code1) p + geom_vline(aes(xintercept = n.mean), mean.data,col="red") # END R CODE ################################################## I can´t figure out why the second example does not work when having the "scales=free" argument, and why I get the extra facets when removing it. Is this a bug? Any help will be very welcomed. Julian -- Julian Mariano Burgos Hafrannsóknastofnunin/Marine Research Institute Skúlagata 4, 121 Reykjavík, Iceland Sími/Telephone : +354-5752037 Bréfsími/Telefax: +354-5752001 Netfang/Email: jul...@hafro.is, jmbur...@uw.edu ______________________________________________ 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.