gls aic variance can gls model have multiple covariates is the variable structure best for a variable gls? ls variance with multiple covariates what type of variance structure is best for gls models can a continuous predictor be used purely for a variance how many covariates do you need to use gls can i use a multiple covariata model in glis can you use variance structure in gls how many variance in linear model how do you get the lowest aic in gls model is gls a variable structure how to build a gls variance structure gls variance structure can you have multiple variables in variance structure can a fixed variance be used with multiple coefficients is gls a variable structure how to use multiple covariate variance structure in mixed effects why does a variable structure differ from that of gls? what is variance structure for gls