Distribution from a Histogram

Hi All,

I have the following histogram which has been generated from my data. But I am unable to fix this to a distribution; because of the negative values I am unable to create a lognormal or Weibull distribution. Any ideas on how to do this?

[Jan]

This is not twitter: No # characters in tag names. Thanks.

Answer 1

[Belita Kin]

(As others have pointed out, a Weibull distribution is not likely to be an appropriate approximation when the data are integers only. The following is intended just to help you determine what that previous researcher did, rightly or wrongly.) There are several alternative methods that are not affected by zeros in the data, such as using various method-of moments estimators. These typically require numerical solution of equations involving the gamma function, because the moments of the Weibull distribution are given in terms of this function. I'm not familiar with R, but here's a Sage program that illustrates one of the simpler methods -- maybe it can be adapted to R? (You can read about this and other such methods in, e.g., "The Weibull distribution: a handbook" by Horst Rinne, p. 455ff -- however, there is a typo in his eq.12.4b, as the '-1' is redundant). Check for fast custom online