On 2010-08-24 11:06, Mike Williamson wrote:
Hello All,Using the standard "summary" function in 'R', I ran across some odd behavior that I cannot understand. Easy to reproduce: Typing: summary(c(6,207936)) Yields:: Min. *1st Qu. Median Mean 3rd Qu. Max.* 6 *51990 104000 104000 156000 207900* None of these values are correct except for the minimum. If I perform "quantile(c(6, 207936))", it gives the correct values. I originally presumed that summary was merely calling "quantile" if it saw a numeric, but this doesn't seem to be the case. Anyone know what's going on here? On a related note, what is the statistically correct answer for calculating the 1st quartile& 3rd quartile when only 2 values are present? I presume one takes the mid-point between the median (also calculated) and the min or max. So in this case, 51988.5 for 1st& 155953.5 for 3rd (which is what quantile calculates). But taking 25%& 75% of the sum of the 2 also seems "reasonable". Either way, "summary" is calculating the wrong number, and most disturbing is that it mis-calculates the max. Regards, Mike
This is one of those (many) situations where reading the help pages really helps nicely: help(summary) points you to the 'digits' argument (as David has said) and that probably defaults to 'digits=4' for you. So, no, R is not miscalculating anything. help(quantile) shows that there are quite a few ways to define quantiles and that R defaults to 'type=7'. -Peter Ehlers ______________________________________________ [email protected] 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.
