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From |
"Joao Ricardo F. Lima" <jricardofl@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Why the square of a negative number is still negative |

Date |
Fri, 16 Dec 2011 13:38:50 -0300 |

Tiago, from the NC151 - "An introduction to Stata Programming": "Because, when Stata is executing lines, it does the following: 1. substitutes for any and all macros 2. executes the line If the value contained in the macro b happened to be negative, the operator precedence would have evaluated the power operator first and then the negation operator. So, macros are not the same as variables in other programming languages. They are exactly like macros in the C language in this sense. Ensuring the proper order of algebraic operations is the responsibility of the programmer (you). So, none of you should now be surprised if you type in the following: local b = -2 di `b'^2 " HTH, Joao Lima Em 16 de dezembro de 2011 13:31, Tiago V. Pereira <tiago.pereira@mbe.bio.br> escreveu: > Dear statalisters, > > Can someone explain why is this happening?: > > local x = -2 > */Approach A: > dis (`x'^2)*(5) > */Approach B: > dis (`x'*`x')*(5) > */Approach C: > dis ((`x')^2)*(5) > > > My output is: > > . dis (`x'^2)*(5) > -20 > > . */Approach B: > > . dis (`x'*`x')*(5) > 20 > > . */Approach C: > > . dis ((`x')^2)*(5) > 20 > > > Do I need vacations? (Am I forgetting something very simple from > mathematics?) > > All the best, > > Tiago > > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ -- --------------------------------------------------------- João Ricardo F. de Lima Pesquisador A - Economia Aplicada Embrapa Semiárido e-mail: joao.ricardo@cpatsa.embrapa.br fone: +55 (87) 3866-3667 home-page: www.cpatsa.embrapa.br ---------------------------------------------------------- * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: Why the square of a negative number is still negative***From:*"Tiago V. Pereira" <tiago.pereira@mbe.bio.br>

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