Re: [R] find position Try match(0.4, a) Also see ?match and the nomatch= argument, in particular. If your numbers are only equal to within an absolute tolerance, tol, as discussed in the R FAQ    http://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-doesn_0027t-R-think-these-numbers-are-equal_003f you may need:    tol <- 1e-6    match(TRUE, abs(a-0.4) < tol) or    which(abs(a-0.4) < tol)[1]  # tol from above and analogously if a relative tolerance is required. On 6/10/07, gallon li  wrote: > find the position of the first value who equals certain number in a vector: > > Say a=c(0,0,0,0,0.2, 0.2, 0.4,0.4,0.5) > > i wish to return the index value in a for which the value in the vector is > equal to 0.4 for the first time. in this case, it is 7. > >        [[alternative HTML version deleted]] > > ______________________________________________ > R-help@stat.math.ethz.ch 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. > ______________________________________________ R-help@stat.math.ethz.ch 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.