Suggest you contact the package maintainer. ?maintainer
Cheers, Bert Bert Gunter "The trouble with having an open mind is that people keep coming along and sticking things into it." -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip ) On Thu, Jul 26, 2018 at 9:49 AM, john matthew via R-help < r-help@r-project.org> wrote: > Hello all, > > I am using the samplesize package (n.ttest function) to calculate > number of samples per group power analysis (t-tests with unequal > variance). > I can break this n.ttest function from the samplesize package, > depending on the standard deviations I input. > > This works very good. > > n.ttest(sd1 = 0.35, sd2 = 0.22 , variance = "unequal") > # outputs > $`Total sample size` > [1] 8 > > $`Sample size group 1` > [1] 5 > > $`sample size group 2` > [1] 3 > > Warning message: > In n.ttest(sd1 = 0.35, sd2 = 0.22, variance = "unequal") : > Arguments -fraction- and -k- are not used, when variances are unequal > The warnings are fine and all is good. > > > But if I run it again with. > n.ttest(sd1 = 1.68, sd2 = 0.28 , variance = "unequal") > # outputs > Error in while (n.start <= n.temp) { : > missing value where TRUE/FALSE needed > In addition: Warning messages: > 1: In n.ttest(sd1 = 1.68, sd2 = 0.28, variance = "unequal") : > Arguments -fraction- and -k- are not used, when variances are unequal > 2: In qt(conf.level, df = df_approx) : NaNs produced > 3: In qt(power, df = df_approx) : NaNs produced > > It breaks. > The first obvious thing is that the standard deviations are a lot > different in the 2nd example that breaks, compared with the first run. > > Checking the code myself, I can see it breaks down when the variable > "df_approx" becomes a negative number, in a while loop from the > n.ttest function. > Exert of the code I am talking about. > > while (n.start <= n.temp) { > n.start <- n1 + n2 + 1 > n1 <- n.start/(1 + k) > n2 <- (k * n.start)/(1 + k) > df_approx <- 1/((gamma)^2/(n1 - 1) + (1 - gamma)^2/(n2 - 1)) # > this calculation becomes negative and breaks subsequently > tkrit.alpha <- qt(conf.level, df = df_approx) > tkrit.beta <- qt(power, df = df_approx) > n.temp <- ((tkrit.alpha + tkrit.beta)^2)/(c^2) > } > > I can hard code df_approx to be an absolute value but I don't know if > that messes up the statistics. > > Can anyone help or any ideas? How to fix? > > John. > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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. > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.