From: John Fox <jfox_at_mcmaster.ca>

Date: Wed, 18 Feb 2009 17:27:51 -0500

R-devel_at_r-project.org mailing list

https://stat.ethz.ch/mailman/listinfo/r-devel Received on Wed 18 Feb 2009 - 21:34:17 GMT

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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