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## Re: [igraph] fitting a straight line to power-law distribution

**From**: |
Fabio Daolio |

**Subject**: |
Re: [igraph] fitting a straight line to power-law distribution |

**Date**: |
Thu, 28 Jul 2011 11:42:01 +0200 |

Hi Narcis,
that is because, if I got it right, when a probability density function p(x) is
power-law
with an exponent alpha, i.e. p(x)~x^(-alpha),
then its complementary cumulative distribution function is also power-law (just
do
the integration from x to infinity) but with exponent -alpha+1, i.e.
P(x)~x^(-alpha+1)
On that note, I've been pointed out to a good paper about fitting empirical data
http://arxiv.org/abs/0706.1062
Sincerely,
--
Fabio
On Jul 28, 2011, at 11:25 AM, Narges Zarrabi wrote:
>* Hi,*
>* *
>* I am trying to understand the fitting to the power law distribution in the *
>* example in link below:*
>* http://igraph.sourceforge.net/screenshots2.html#8*
>* *
>* However, in the following line of the example:*
>* lines(10:500, 10*(10:500)^(-coef(alpha)+1))*
>* *
>* I don't understand why +1 is added in the power (-coef(alpha)+1)*
>* *
>* Could anyone explain the reason ? Thanks*
>* *
>* Regards,*
>* Narcis*
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