Thanks for the answer and for the link. I was lookin for a search trough the forum posts....
So the slope of the line is not important as long as the data is approx. on the line? Thanks, m -----Original Message----- From: Joshua Wiley [mailto:jwiley.ps...@gmail.com] Sent: Saturday, April 30, 2011 8:04 PM To: Matevž Pavlič Cc: r-help@r-project.org Subject: Re: [R] QQ plot for normality testing Hi, qqnorm basically plots your actual sample values against what the values would be (approximately) if they were from a normal distribution. qqline() adds a line through the 1st and 3rd quartiles. So roughly speaking, if your QQ plot forms a straight line (particularly the one drawn by qqline), then your sample values match a normal distribution. With real data, it is typically not a "yes/no" decision, rather "is my data normal enough?" Questions like this have been asked many times on this list, so searching the mailing list archives will lead you to many more discussions and suggestions. Here is one way to search: http://tolstoy.newcastle.edu.au/R/ Cheers, Josh On Sat, Apr 30, 2011 at 10:27 AM, Matevž Pavlič <matevz.pav...@gi-zrmk.si> wrote: > Hi all, > > > > I am trying to test wheater the distribution of my samples is normal with QQ > plot. > > > > I have a values of water content in clays in around few hundred samples. Is > the code : > > > > qqnorm(w) #w being water content > > qqline(w) > > > > > > sufficient? > > > > How do I know when I get the plots which distribution is normal and which is > not? > > > > Thanks, m > > > [[alternative HTML version deleted]] > > ______________________________________________ > 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. -- Joshua Wiley Ph.D. Student, Health Psychology University of California, Los Angeles http://www.joshuawiley.com/ ______________________________________________ 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.
