[R] Strange warning in summary.lm

[ONKELINX, Thierry]

Dear useRs,

Lately I noticed a strange warning in the summary of a lm-object. Any
idea what this warning is about? I'm using R 2.5.1 on Win XP pro.

> x <- rnorm(100)
> y <- rnorm(100)
> summary(lm(y~x))

Call:
lm(formula = y ~ x)

Residuals:
     Min       1Q   Median       3Q      Max 
-1,77809 -0,68438 -0,04409  0,63891  2,30863 

Coefficients:
            Estimate Std. Error t value Pr(>|t|)
(Intercept) -0,00217    0,09244  -0,023    0,981
x            0,01315    0,09628   0,137    0,892

Residual standard error: 0,9236 on 98 degrees of freedom
Multiple R-Squared: 0.0001903,  Adjusted R-squared: -0.01001 
F-statistic: 0.01866 on 1 and 98 DF,  p-value: 0,8916 

Warning message:
NAs introduced by coercion in: as.double.default(Cf[okP]) 

	
Thanks,

Thierry

------------------------------------------------------------------------
----
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature
and Forest
Cel biometrie, methodologie en kwaliteitszorg / Section biometrics,
methodology and quality assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium
tel. + 32 54/436 185
Thierry.Onkelinx op inbo.be
www.inbo.be 

Do not put your faith in what statistics say until you have carefully
considered what they do not say.  ~William W. Watt
A statistical analysis, properly conducted, is a delicate dissection of
uncertainties, a surgery of suppositions. ~M.J.Moroney