Hey :) In addition, although (-2)^3 = -8, (-8)^(1/3) != -2, mathematically. A fractional power of a negative number is complex. And this can be obtained properly in R:
> (-8+0i)^(1/3) [1] 1+1.732051i Cheers, Tsjerk >> This is some interesting: >> >>> -8^(1/3) >> >> [1] -2 >> >>> x=(-8:8) >> >>> y=x^(1/3) >> >>> y >> >> [1] NaN NaN NaN NaN NaN NaN NaN >> NaN >> 0.000000 1.000000 >> >> [11] 1.259921 1.442250 1.587401 1.709976 1.817121 1.912931 2.000000 >> So, can anybody explain this?! (Why is x[1]^(1/3)=y[1]=NaN, but >> -8^(1/3)=-2?) >> > > Operator precedence. > > See R FAQ 7.33 Why are powers of negative numbers wrong? > > > Berend > > > -- > View this message in context: > http://r.789695.n4.nabble.com/cube-root-tp3455020p3455027.html > Sent from the R help mailing list archive at Nabble.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. > -- Tsjerk A. Wassenaar, Ph.D. post-doctoral researcher Molecular Dynamics Group * Groningen Institute for Biomolecular Research and Biotechnology * Zernike Institute for Advanced Materials University of Groningen The Netherlands ______________________________________________ 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.
