Thank you Jim and David for your help. The 'levels' call is not a misdirection, in my actual dataset it is necessary because the flows aren't symmetrical. So while your solution is quite elegant David, it doesn't apply to my actual data, just the example. Too bad, it's quite nice!
I do think that "color.scale.lines" can work, now I just need to figure out how! Unfortunately when I tried your example Jim: date=c(1:300) flow=sin(2*pi/53*c(1:300)) levels=c(rep(c("high","med","low"),100)) data=cbind.data.frame(date, flow, levels) plot(data$date,data$flow,type="n") library(plotrix) color.scale.lines(data$date,data$flow, col=color.scale(data$flow,extremes=c("blue","red"))) I got this error: "Error in length(redrange) : 'redrange' is missing" But I do think the function is the way to go for my dataset. Thank you! -Pam -- View this message in context: http://r.789695.n4.nabble.com/Help-with-plotting-a-line-that-is-multicoloured-based-on-levels-of-a-factor-tp3385857p3412310.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.