There is a problem built into your question: you are treating carb graphically as a continuous variable, yet by asking for a line plot of mean values you seem to be assuming it is discrete. Below are several possible interpretations of your intent.
Continuous: library(ggplot2) p <- ggplot( mtcars, aes( x=carb, y=mpg ) ) + geom_point() p + stat_summary( geom="ribbon", fun.ymin="min", fun.ymax="max" ) p2 <- p + stat_summary( geom="ribbon" , fun.ymin="min" , fun.ymax="max" , alpha=0.2 , fill="blue" ) # local regression p + geom_smooth() # literal interpretation p2 + geom_hline( yintercept = mean( mtcars$mpg ), colour="red" ) # linear regression p2 + geom_smooth( method="lm", se=FALSE, colour="red" ) Discrete: mtcarsmean <- aggregate( mtcars$mpg, mtcars[ , "carb", drop=FALSE ], mean ) # discrete means p2 + geom_line( data=mtcarsmean, mapping=aes( x=carb, y=x ), colour="red" ) The reason this has to be done explicitly outside of the geom_smooth mechanism is because of this conflict between graphically continuous and conceptually discrete data. -- Sent from my phone. Please excuse my brevity. On December 22, 2015 11:43:23 PM PST, pushan chakraborty <pushan.zool...@gmail.com> wrote: >Dear list > >I want to put a line command in the following and also want to >attribute >colour in the geom line command line. It would be a ribbon plot showing >the >mean line. Is there any help? > > >p <- ggplot(mtcars, aes(x=carb, y=mpg)) + geom_point() > >p + stat_summary(geom="ribbon", fun.ymin="min", fun.ymax="max") > >p + stat_summary(geom="ribbon", fun.ymin="min", fun.ymax="max", > alpha=0.2, fill="blue") > > > > > >-- >Pushan Chakraborty >CSIR - SRF > >Center for Pollination Studies, University of Calcutta >35, Ballyguanje Circular Road, Kolkata - 700019 > & >Wildlife Institute of India >Chandrabani, Dehradun - 248001 > >webpage: > >http://cpscu.in/?page_id=51 > >Skype: cpushan > > [[alternative HTML version deleted]] > >______________________________________________ >R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >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. [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
