[R-sig-eco] Continuous distribution for zero or positive values (in GLM or GLMM)

Fred Takahashi fredtaka at gmail.com
Wed May 18 17:46:33 CEST 2011

Hello, just a basic question: what distribution I should use to
analyze continuous data which can had zero or positive values (eg.
mass of grasses in plots assuming that zero mass is meaningful)? My
expected analysis is in the framework of GLM or GLMM (or
alternatively, GAM / GAMM).

One idea I had is to add 0.0001 to all values and use family=Gamma.
That is a good approach?

If a better choice is to use a different distribution, suggestions of
packages to do that are welcome.

Fred Takahashi
Universidade de Brasília - Brasil

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