[R] linear regression
Donald Lehmann
donald.lehmann at pharmacology.oxford.ac.uk
Mon Aug 9 11:25:43 CEST 2004
Dear Consultant
I've done linear regression successfully on R a few times before. But this
time it keeps telling me:-
"Error in lm.fit(x, y, offset = offset, singular.ok = singular.ok, ...) :
0 (non-NA) cases"
The model is:-
fm1 <- lm(TS.CM ~ AGE + SEX + HFE.Y.01 + TFC2B.01 + HFE.Y.01*TFC2B.01, data
= IRONresults, subset = DIAG2.1D == 0)
summary (fm1)
TS.CM is a continuous variable (%s), sex is coded 0 = women, 1 = men,
DIAG2.1D is coded 0 = non-demented, 1 = ALzheimer's disease and the genes,
HFE.Y.01 & TFC2B.01, are coded 0 = non-carrier and 1 = carrier
I've tried recoding the data to use 1 & 2, instead of 0 & 1, and I've
removed the rows with missing data. I've also tried putting "...lm(formula
= TS.CM ~ ..." But I always get the same error message
What am I doing wrong?
A related question: what's the minimum no of data points for regression
analysis to work? We have only 23 cases carrying both genes out of 447 and
only 8 out of 264 in the above subset (ie non-demented). I seem to
remember hearing somewhere that you needed a minimum of ~30 (?), so
probably this wouldn't work anyway. Still, I'd like to know what I was
doing wrong!
Many thanks
Donald (Lehmann)
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