Hello, The documentation of nlme::varIdent says this: "the coefficients of the variance function represent the ratios between the variances and a reference variance (corresponding to a reference group level)" However, the parameter estimate shown in the summary output for lme models is the ratio between standard deviations. Could this be clarified in the documentation, e.g., by adding Eq. 5.13 from?Pinheiro and Bates (2000)? -- Dr. Roland Fu? Th?nen-Institut f?r Agrarklimaschutz/ Th?nen Institute of Climate-Smart Agriculture