Hi, I am a bit surprised how approx resolves ties when ties = 'ordered'. In the following two examples I'd expect the first expression to return 1 (not 2). The documentation reads that "that 'f=0' is right-continuous and 'f=1' is left-continuous" so one would expect the argument to matter when resolving ties. Thanks, Vadim -> approx(c(1,1), seq(2), 1, method = "const", rule = 2, f = 1, yleft = NA, ties = "ordered")$y [1] 2 -> approx(c(1,1), seq(2), 1, method = "const", rule = 2, f = 0, yleft = NA, ties = "ordered")$y [1] 2 -> version _ platform i486-pc-linux-gnu arch i486 os linux-gnu system i486, linux-gnu status major 2 minor 4.1 year 2006 month 12 day 18 svn rev 40228 language R version.string R version 2.4.1 (2006-12-18)