Hi, I'm running a calculation in two ways. The first way is to employ vectors and evaluate a function in one go. The second way is to break down the function into pieces and combine the pieces to the final answer.
Algebraically, they should give me the same result. But the final vector differs significantly. I must be missing something very obvious, but I just cannot see it xx <- c(-9.56305825951348, -8.20220288142583, -6.84134750333818, -5.48049212525052, -4.11963674716287) params <- structure(c(-7.9292094394, 4.9549173134, 4.738588416, 101.5743644892 ), .Names = c("LOG_AC50", "HILL_COEF", "INF_ACTIVITY", "ZERO_ACTIVITY" )) yy <- params[4] + (params[3] - params[4])/(1 + 10^(params[1]-xx)^params[2]) t1 <- 10^(params[1]-xx) t2 <- params[3] - params[4] t3 <- (1+t1)^params[2] t4 <- t2/t3; t5 <- params[4] + t4 I would've expected yy and t5 to be the same; yet they are not -- Rajarshi Guha | http://blog.rguha.net NIH Center for Advancing Translational Science ______________________________________________ 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.