Finding that the plots produced by the commands above are slightly different from each other, I tried this:
I got a slightly less than perfect line. I'd have tried regressing the result of
qnorm(seq(80)/81) on the variable that was plotted on the $x$-axis and plotting residuals against the predictor, expecting to see some graceful curve, but for the fact that I don't know what to use as the predictor. Possibly such a residual plot would reveal more than just the graceful S-shaped thing I'd anticipate.
So my question is this: if the thing on the $x$-axis in the plot produced by
qqnorm is not what I get from
qnorm(seq(80)/81) (and what I did shows that indeed it is not), then what is it?