I have 20 variables: 5,9,6,1,5,9,7,4,5,6,3,2,4,8,9,6,1,8,4,8 How do I calculate the corresponding quantiles from a normal distribution with the same mean and variance as the sample? Also, how do I draw a QQ plot of the data? Thanks for any help! -- View this message in context: http://www.nabble.com/Quantiles-and-QQ-plots-tf4925742.html#a14097909 Sent from the R help mailing list archive at Nabble.com.
Your vector: x=c(5,9,6,1,5,9,7,4,5,6,3,2,4,8,9,6,1,8,4,8) Check descriptives: mean(x) sd(x) get quantiles for a normal with mean and standard deviation of x: qnorm(c(0.25,0.5,0.75),mean=mean(x),sd=sd(x)) Output: [1] 3.76997 5.50000 7.23003 to get the quantile plot install library "car" and load library by typing in the R prompt: library(car) qq.plot(x) But you can easily look at the histogram of your vector - hist(x) - to see that this does not look very normal Daniel -----Urspr?ngliche Nachricht----- Von: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] Im Auftrag von alfieim29 Gesendet: Friday, November 30, 2007 6:26 PM An: r-help at r-project.org Betreff: [R] Quantiles and QQ plots I have 20 variables: 5,9,6,1,5,9,7,4,5,6,3,2,4,8,9,6,1,8,4,8 How do I calculate the corresponding quantiles from a normal distribution with the same mean and variance as the sample? Also, how do I draw a QQ plot of the data? Thanks for any help! -- View this message in context: http://www.nabble.com/Quantiles-and-QQ-plots-tf4925742.html#a14097909 Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help at 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.
-----Original Message----- From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of alfieim29 Sent: Saturday, 1 December 2007 9:26 AM To: r-help at r-project.org Subject: [R] Quantiles and QQ plots I have 20 variables: 5,9,6,1,5,9,7,4,5,6,3,2,4,8,9,6,1,8,4,8 [WNV] I think you have 20 values, not variables. How do I calculate the corresponding quantiles from a normal distribution with the same mean and variance as the sample? [WNV] There is some ambiguity about this, but a simple way to do it would be x <- c(5,9,6,1,5,9,7,4,5,6,3,2,4,8,9,6,1,8,4,8) n <- length(x) p <- (1:n - 0.5)/n z <- qnorm(p, mean(x), sd(x))[order(order(x))] Also, how do I draw a QQ plot of the data? [WNV] having done all this you can now just plot(z, x) but a much simpler way is qqnorm(x) qqline(x) and don't bother calculating all that stuff! Thanks for any help! -- View this message in context: http://www.nabble.com/Quantiles-and-QQ-plots-tf4925742.html#a14097909 Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help at 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.