Re: [R] Is it a bug ? I don't get your point, because  > exp(-(-3)^2.2) [1] NaN is correct. A negative value to the power of a non-integer is undefined  in IR. Of course it is defined as a complex number:  > exp(-(-3+0i)^2.2) [1] 1.096538e-04-3.47404e-05i Uwe Ligges Giuseppe PEDRAZZI wrote: > 		[[diverted from R-bugs to R-help by the list maintainer]] >  > Dear Friend and distinguished R gurus, >  > first of all really thank you very much for the marvellous tool that is R. >  > I am using R 2.5.0,  windows XP - italian language. >  > I was perfoming some calculation on fractional exponential and > I found a strange behaviour. I do not know if it is really a bug, but I would expect > a different answer from R. >  > I was trying the following : >  > x <- seq(-3,3, by =0.1) > n <- 2.2 > y <- exp(-x^n) >  > well, the y vector contains (NaN for all negative value of x) >  > but if you ask for single value calculation like >  > y <- exp(-(-3)^2.2) or  >  > y <- exp(-(-2.9)^2.2) >  > the answer is correct.  > It seem it does not make the calculation in vector form. >  > I got the same behaviour (NaN)  in a for loop >  >> for(i in 1:length(x)) y[i]=exp(x[i]^n) >> y >  [1]           NaN          NaN          NaN          NaN          NaN          NaN          NaN          NaN          NaN > [10]          NaN          NaN          NaN          NaN          NaN          NaN          NaN          NaN          NaN > [19]          NaN          NaN          NaN          NaN          NaN          NaN          NaN          NaN          NaN > [28]          NaN          NaN          NaN     1.000000     1.006330     1.029416     1.073302     1.142488     1.243137 > [37]     1.384082     1.578166     1.844237     2.210260     2.718282     3.432491     4.452553     5.936068     8.137120 > [46]    11.473746    16.648415    24.867680    38.251295    60.611092    98.967689   166.572985   289.077778   517.425935 > [55]   955.487320  1820.793570  3581.521323  7273.674928 15255.446778 33050.861013 73982.100407 >  > Is it strange or did I miss something ? >  > Many thanks for the attention. >  >  > Very best regards >  > Giuseppe Pedrazzi > Dept Public Health, Physics Division > University of Parma, Italy > 	[[alternative HTML version deleted]] >  > ______________________________________________ > R-help@stat.math.ethz.ch 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. ______________________________________________ R-help@stat.math.ethz.ch 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.