[R] qqplot

[Peter Flom]

Peter Ehlers <ehlers at ucalgary.ca> wrote
>
>That's not what qqline() does and for good reason - it treats
>x and y asymmetrically.
>
>But qqline() is a very simple function, using the quartiles
>as also suggested by John. Here's a modified version that
>should work for Carol:
>
>qqline2 <- function (x, y, ...)
>{
>     y <- quantile(y[!is.na(y)], c(0.25, 0.75))
>     x <- quantile(x[!is.na(x)], c(0.25, 0.75))
>     slope <- diff(y)/diff(x)
>     int <- y[1L] - slope * x[1L]
>     abline(int, slope, ...)
>}
>
>I've just replaced the line using Normal quantiles with
>the quantiles of x (and omitted the datax option).
>

Peter

Good point.

Peter




Peter L. Flom, PhD
Statistical Consultant
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