From: John Maindonald <John.Maindonald_at_anu.edu.au>

Date: Thu, 19 Feb 2009 08:56:57 +1100

R-devel_at_r-project.org mailing list

https://stat.ethz.ch/mailman/listinfo/r-devel Received on Wed 18 Feb 2009 - 21:00:20 GMT

Date: Thu, 19 Feb 2009 08:56:57 +1100

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.

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

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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