Power functions?
on 01/03/2009 02:32 PM rkevinburton at charter.net wrote:
I had a question about the basic power functions in R. For example from the R console I enter: -1 ^ 2 [1] -1 but also -1^3 [1] -1 -0.1^2 [1] -0.01 Normally pow(-1, 2) return either -Infinity or NaN. Has R taken over the math functions? If so I would think that -1^2 is 1 not -1 and -0.1^2 is 0.01 not -0.01. Thank you. Kevin
Kevin, See R FAQ 7.33 Why are powers of negative numbers wrong? http://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-are-powers-of-negative-numbers-wrong_003f For the issue of returning -Inf or NaN, I suspect that you are thinking about negative numbers being raised to non-integer powers. For example, taking into consideration the enlightenment in the above FAQ:
(-1) ^ (1 / 2)
[1] NaN
(-2) ^ (1/2)
[1] NaN
sqrt(-2)
[1] NaN Warning message: In sqrt(-2) : NaNs produced
(-2) ^ 2.5
[1] NaN HTH, Marc Schwartz