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

[Chris Evans]

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 at 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 ***