Hi everyone,

i'm using glm() to analyze a dataset where I have herbivory values expressed
as percentage (values between 0 and 1).
Some plants were sampled in 3 different occasions. The thing is that the
number of sampled plants differs among the samples and I want to verify
whether herbivory % differs among the samples.
Pretty simple, right?

But i'm facing a problem when choosing weights: should I give column
"weight" the number of species in that same sample, like this>

Sample  //    Herbivory    //    Weight
Jan                   ..                     3
Jan                                          3
Jan                                          3
Feb                                          4
Feb                                          4
Feb                                          4
Feb                                          4
Apr                                          5
Apr                                          5
Apr                                          5
Apr                                          5
Apr                                          5

or should i leave weights out of the formula, as R supposedly takes it into
account?

just as reference, im using glm(herbivory~sample, quasibinomial,
weights=weight)
and again, my data is already converted as proportions, so numbers aren't
noted as 2%, but as 0,02.


Thanks in advance and best wishes from Brazil.
-----------------------------------------
Claudio Magalhaes
Cientista Ambiental
LIPA - Lab. de Interações Planta-Animal
Programa de Pós-Graduação em Biologia Vegetal - UFPE
+558188694866

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