[R-sig-ME] Interpreting variances in lme with varIdent weights

ONKELINX, Thierry Thierry.ONKELINX at inbo.be
Tue Jul 30 12:40:56 CEST 2013

Dear Ellison,

Correlation and variance structures in nlme work only on the residuals, not on the random effects.

Best regards,


ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature and Forest
team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
Kliniekstraat 25
1070 Anderlecht
+ 32 2 525 02 51
+ 32 54 43 61 85
Thierry.Onkelinx op inbo.be

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~ Sir Ronald Aylmer Fisher

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-----Oorspronkelijk bericht-----
Van: r-sig-mixed-models-bounces op r-project.org [mailto:r-sig-mixed-models-bounces op r-project.org] Namens S Ellison
Verzonden: dinsdag 30 juli 2013 12:32
Aan: r-sig-mixed-models op r-project.org
Onderwerp: [R-sig-ME] Interpreting variances in lme with varIdent weights

 We've managed to get ourselves confused in interpreting lme's output and would appreciate clarification; I and a colleague differ on interpreting the words used in lme's help pages and output, and I see his point; it can be read two ways.

Using varIdent weights, lme provides a factor for each varIdent stratum. The question is whether that factor applies to standard deviations for _all_ random effects or just to the sd for the residual term within each stratum.

Any guidance appreciated.

S Ellison

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