Mixed effects models and extensions in ecology with R by Alain F. Zuur Elena N. Ieno Neil Walker Anatoly A. Saveliev & Graham M. Smith

Author:Alain F. Zuur, Elena N. Ieno, Neil Walker, Anatoly A. Saveliev & Graham M. Smith
Language: eng
Format: epub
Publisher: Springer New York, New York, NY

A similar graph was drawn for the count data. In this case, fitted values are obtained from Equation (11.23). Regression coefficients were taken from the upper part of the summary(Nb1B) output. Area 4 in 1999 and 2000 has the highest values. This information can also be derived from the estimated regression parameters; so the need for a graph is limited.

11.5 ZAP and ZANB Models, Alias Hurdle Models

In the previous section, we assumed the zeros for the cod data consist of false zeros and true zeros. In this section, we do not discriminate between the four types of zeros; they are just zeros.

We follow the same approach as in Section 11.2; first we present the probability functions for the two-part models and give the maximum likelihood equations in Section 11.5.1, and an example plus the R code is presented in Section 11.5.2. If you are not interested in the underlying mathematics, just read the summary at the end of Section 11.5.1.

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