# cube root

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## cube root

 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?)   Thx!!!             [[alternative HTML version deleted]] ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: cube root

 ?Syntax for precedence of operators. On 16/04/11 22.51, Branimir K. Hackenberger wrote: > 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?) > > > > Thx!!! > > > > > > > [[alternative HTML version deleted]] > > ______________________________________________ > [hidden email] 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. -- Niels Richard Hansen                     Web:   www.math.ku.dk/~richard Associate Professor                      Email: [hidden email] Department of Mathematical Sciences             [hidden email] University of Copenhagen                 Skype: nielsrichardhansen.dk Universitetsparken 5                     Phone: +1 510 502 8161 2100 Copenhagen Ø Denmark ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: cube root

 In reply to this post by Branimir Hackenberger Branimir K. Hackenberger wrote 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
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## Re: cube root

 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. > > ______________________________________________ > [hidden email] 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 ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.