Re: [Rd] plot.lm: "Cook's distance" label can overplot point labels

From: John Fox <jfox_at_mcmaster.ca>
Date: Wed, 18 Feb 2009 17:27:51 -0500

Dear John,

> -----Original Message-----
> From: John Maindonald [mailto:John.Maindonald_at_anu.edu.au]
> Sent: February-18-09 4:57 PM
> To: John Fox
> Cc: 'Martin Maechler'; r-devel_at_r-project.org
> Subject: Re: [Rd] plot.lm: "Cook's distance" label can overplot point
labels
>
> Dear John -
> The title above the graph is also redundant for the first of the
> plots; do we want to be totally consistent? I am not sure.

Why not? "A foolish consistency is the hobgoblin of little minds," but maybe this isn't a foolish consistency.

>
> It occurs to me that the text "Cook's distance", as well as the
> contours, might be in red.

That would provide a nice visual cue (for those who aren't colour blind).

Best,
 John

> Regards
> John.
>
> John Maindonald email: john.maindonald_at_anu.edu.au
> phone : +61 2 (6125)3473 fax : +61 2(6125)5549
> Centre for Mathematics & Its Applications, Room 1194,
> John Dedman Mathematical Sciences Building (Building 27)
> Australian National University, Canberra ACT 0200.
>
>
> On 18/02/2009, at 12:27 PM, John Fox wrote:
>
> > Dear John,
> >
> > It occurs to me that the title above the graph, "Residuals vs.
> > Leverage," is
> > entirely redundant since the x-axis is labelled "Leverage" and the y-
> > axis
> > "Studentized residuals." Why not use the title above the graph for
> > "Cook's
> > distance countours"?
> >
> > Regards,
> > John
> >
> >> -----Original Message-----
> >> From: r-devel-bounces_at_r-project.org
[mailto:r-devel-bounces_at_r-project.org
> >> ]
> > On
> >> Behalf Of John Maindonald
> >> Sent: February-17-09 5:54 PM
> >> To: r-devel_at_r-project.org
> >> Cc: Martin Maechler
> >> Subject: [Rd] plot.lm: "Cook's distance" label can overplot point
> >> labels
> >>
> >> The following code demonstrates an annoyance with plot.lm():
> >>
> >> library(DAAGxtras)
> >> x11(width=3.75, height=4)
> >> nihills.lm <- lm(log(time) ~ log(dist) + log(climb), data = nihills)
> >> plot(nihills.lm, which=5)
> >>
> >> OR try the following
> >> xy <- data.frame(x=c(3,1:5), y=c(-2, 1:5))
> >> plot(lm(y ~ x, data=xy), which=5)
> >>
> >> The "Cook's distance" text overplots the label for the point with the
> >> smallest residual. This is an issue when the size of the plot is
> >> much
> >> less than the default, and the pointsize is not reduced
> >> proportionately.
> >>
> >>
> >> I suggest the following:
> >> xx <- hii
> >> xx[xx >= 1] <- NA
> >> ## Insert new code
> >> fracht <- (1.25*par()$cin[2])/par()$pin[2]
> >> ylim[1] <- ylim[1] - diff(ylim)*max(0, fracht-0.04)
> >> ## End insert new code
> >> plot(xx, rsp, xlim = c(0, max(xx, na.rm = TRUE)),
> >> ylim = ylim, main = main, xlab = "Leverage",
> >> ylab = ylab5, type = "n", ...)
> >>
> >> Then, about 15 lines further down, replace
> >> legend("bottomleft", legend = "Cook's distance",
> >> lty = 2, col = 2, bty = "n")
> >>
> >> by
> >> legend("bottomleft", legend = "Cook's distance",
> >> lty = 2, col = 2, bty = "n", y.intersp=0.5)
> >>
> >> If this second change is not made, then one wants fracht <-
> >> (1.5*par()
> >> $cin[2])/par()$pin[2]
> >> I prefer the "Cook's distance" text to be a bit closer to the x-axis,
> >> as it separates it more clearly from any point labels.
> >>
> >> John Maindonald email: john.maindonald_at_anu.edu.au
> >> phone : +61 2 (6125)3473 fax : +61 2(6125)5549
> >> Centre for Mathematics & Its Applications, Room 1194,
> >> John Dedman Mathematical Sciences Building (Building 27)
> >> Australian National University, Canberra ACT 0200.
> >>
> >> ______________________________________________
> >> R-devel_at_r-project.org mailing list
> >> https://stat.ethz.ch/mailman/listinfo/r-devel
> >
> >



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