[R] lme4: Error in getResponseFormula(form) : "Form" must be a two sided formula

From: Chris Evans <stats_at_psyctc.org>
Date: Tue 07 Feb 2006 - 09:29:59 EST


I'm sure I'm being stupid so flame away...

R2.2.1 on Windoze (boohoo) latest updates of packages.

I'm exploring a dataset (land) with three variables looking at an narrowly unbalanced two group (GROUP) ANCOVA of a randomised controlled trial analysing endpoint score (SFQ.LOCF.ENDPOINT) entering the baseline score (SFQ.BASELINE) as covariate and the following work fine:

> res.same <- lm(SFQ.LOCF.ENDPOINT ~ SFQ.BASELINE + GROUP,land)
> res.diff <- lm(SFQ.LOCF.ENDPOINT ~ SFQ.BASELINE + GROUP + SFQ.BASELINE*GROUP,land)
> anova(res.same,res.diff)

I try:

> lmList(SFQ.LOCF.ENDPOINT ~ SFQ.BASELINE | GROUP, land)
Call:
Error in getResponseFormula(form) : "Form" must be a two sided formula

I'm puzzled. That looks like a two sided formula very like the one in the help for lme4 (which had been loaded) and the data look OK:

> table(land$SFQ.LOCF.ENDPOINT)

 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 23  1 1 2 4 8 5 16 9 7 14 18 7 16 9 6 8 4 6 2 3
> table(land$SFQ.BASELINE)

 3 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23  1 1 3 3 4 11 7 7 10 12 9 16 14 9 8 7 8 6 1 1
> table(land$GROUP)

 1 2
87 89

Advice accepted gratefully and flames ruefully!

Chris

-- 
Chris Evans <chris@psyctc.org>
Consultant Psychiatrist in Psychotherapy, Rampton Hospital; 
Research Programmes Director, Nottinghamshire NHS Trust, 
Hon. Professor of Psychotherapy, Nottingham University,
Hon. SL Institute of Psychiatry
*** My views are my own and not representative of those institutions ***

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Received on Tue Feb 07 09:37:46 2006

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