[R] Heteroscedasticity in a percent-cover dataset

Lai Wen Ya Samantha s.lai at u.nus.edu
Fri Apr 15 07:49:12 CEST 2016


I am currently trying to do a GLMM on a dataset with percent cover of
seagrass (dep. var) and a suite of explanatory variables including algal
(AC) and epiphyte cover (EC), rainfall, temperature and sunshine hours.


As the dependent variable is percent cover, I used a binomial error
structure. I also have a random effect due to nested of the data collection
strategy. However, I keep getting heteroscedasticity issues as shown in the
image below. I have tried using an arcsine transformation (with a lme), but
the scatter of residuals are still very much similar.

What else can I do to try to resolve the heteroscedasticity in my data? Any
help will be very much appreciated!



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