[Rd] plot.lm mislabels points with na.exclude (PR#3750)

richard_raubertas at merck.com richard_raubertas at merck.com
Fri Aug 15 01:38:29 MEST 2003

R 1.7.1 on Windows XP

The "normal Q-Q plot" produced by plot.lm() mislabels points 
when the model is fitted using na.action=na.exclude.  Example:

x <- 1:50
y <- x + rnorm(50)
y[c(5,10,15)] <- NA   # insert some NA's
y[40] <- 50  # add an outlier
plot(lm(y ~ x, na.action=na.omit))  # outlier correctly labeled in all 
                                    # four plots
plot(lm(y ~ x, na.action=na.exclude)) # labels attached to wrong points
                                      # in the QQ plot (only)

Rich Raubertas
Biometrics Research
Merck & Co.

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