Hi there, This is now the code
%%%%% library(grid) vp <- viewport( x = unit(0, "npc"), y = unit(0, "npc"), just = c("left", "bottom"), xscale = c(-1, 1) , yscale = c(-1, 1)) vp2 <- viewport( # probably not needed but I had trouble placing the xaxis x = unit(0, "npc"), y = unit(0.5, "npc"), just = c("left", "bottom"), xscale = c(-1, 1) , yscale = c(-1, 1)) pushViewport(vp) grid.xaxis(at=seq(-1, 1, by=0.2), label=FALSE, vp=vp2) grid.points(x=0.3, y=0.5, gp=gpar(col=NA), default.units = "npc", name="h1", vp=vp) grid.points(x=0.7, y=0.5, gp=gpar(col=NA), default.units = "npc", name="h2", vp=vp) grid.text("s", x=0.3, y=unit(-1, "lines"), vp=vp2) grid.text("t", 0.7, unit(-1, "lines"), gp=gpar(col="red"), vp=vp2) grid.text("mu(s,t)", 0.5, unit(5, "lines"), vp=vp2) grid.curve(grobX("h2", 180), grobY("h2", 180), grobX("h1", 180), grobY("h1", 180), shape=1, ncp=10, square=FALSE, curvature=.4, arrow=arrow(angle=20,ends="first") ) upViewport() %%%%% for this line: grid.text("mu(s,t)", 0.5, unit(5, "lines"), vp=vp2) how do I change "mu(s,t)" to the expression "mu"? I have tried grid.text(expression="mu(s,t)", 0.5, unit(5, "lines"), vp=vp2) grid.text(expression(mu(s,t)), 0.5, unit(5, "lines"), vp=vp2) both didnt work AND when I tried to save the output as PDF file it returns: Error in function (name) : Grob 'h2' not found I have no idea what to do? -- View this message in context: http://www.nabble.com/curvedarrow-%28some-graphics-problem%29-tp24158796p24196544.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.