[R] linear regression

Donald Lehmann
Mon, 09 Aug 2004 09:25:43 -0000

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)