[R-sig-eco] glm for ratio [0,1] data

[Rubén Roa Ureta]

Bálint Czúcz wrote:
> Dear List,
>
> does anyone know a good way to perform GLM on ratio data (i.e. data
> between 0 and 1)? Binomial GLM is quite straightforward to use if you
> have integer numbers for successes/failures. But how to proceed if you
> only have the ratio? This can occur in a multitude of ways, e.g the
> response variable is the estimated cover of a species, percentage of
> canopy lost, etc.
>   
There is a glm-ish approach to model data in the interval (0,1) using 
the Beta distribution and the betareg function of the betareg package.
See also:
Ferrari, S.L.P., Cribari-Neto, F. 2004. Beta regression for modelling 
rates and proportions. Journal of Applied Statistics 31(7):799-815.

HTH

Rubén