[R] possible issue with scatterplot function in car package

[Yousri Fanous]

Thank you Professor John for your answer.

As you rightly said I am not using the ch in my example report as it has no
bearing to the issue.
However it is the ch that led me to find the issue.
I was trying to label each point with its corresponding aa$ch value.
I used this code:

scatterplot(aa$x,aa$y,smooth = FALSE, grid = FALSE, frame = FALSE,regLine=F)
text(aa$x,aa$y, labels=aa$ch,font=1 ,cex=.9,pos=3)

The annotation was correct for 4 points but not for the (2,5) point.
I figured it is because it is close to the margin of the plot hence as a
quick solution I modified xlim to shift the point away from the margin.
This worked for the annotation but eventually led to the issue I described.

Thank you so much for your time

Yousri Fanous

Software Developer
IBM CANADA

On Sat, May 2, 2020 at 11:47 PM Fox, John <jfox using mcmaster.ca> wrote:

>
> Dear Yousri,
>
> Yes, this is clearly a bug, and almost surely a long-standing one. We'll
> fix it in the next release of the car package.
>
> BTW, stringsAsFactors defaults to FALSE in R 4.0.0 (and you don't use the
> ch variable in the example). Also, although it has no bearing on the bug,
> I'd generally prefer
>
>         scatterplot(y ~ x, data=aa, smooth=FALSE, grid=FALSE,
>                 frame=FALSE, regLine=FALSE, xlim=c(0, 8))
>
> Thank you for the bug report,
>  John
>
>   -----------------------------
>   John Fox, Professor Emeritus
>   McMaster University
>   Hamilton, Ontario, Canada
>   Web: http::/socserv.mcmaster.ca/jfox
>
> > On May 2, 2020, at 7:30 PM, Yousri Fanous <yousri.fanous using gmail.com>
> wrote:
> >
> > library (car)
> >
> > aa <- data.frame(x=c(2,  5, 6, 7, 8),
> > +  y=c(5,  10, 9, 12, 11),
> > + ch=c("N",  "Q", "R", "S", "T"),
> > + stringsAsFactors=FALSE)
> >
> > scatterplot(aa$x,aa$y,smooth = FALSE, grid = FALSE, frame =
> FALSE,regLine=F)
> >
> > Both x and y boxplots are correct
> > and in particular the median of the x box is at 6 which is confirmed
> >
> >> median(aa$x)
> > [1] 6
> >
> > Now I do only one addition to the scatterplot: I add xlim
> >> scatterplot(aa$x,aa$y,smooth = FALSE, grid = FALSE, frame =
> > FALSE,regLine=F,xlim=c(0,8))
> >
> > This causes the boxplot on x-axis to be in error:
> > 1) the lower whisker starts now from zero
> > 2) the median is between 4 and 6 and no longer at 6 as before
> >
> >> sessionInfo()
> > R version 3.6.3 (2020-02-29)
> > [1] car_3.0-7
> >
> >       [[alternative HTML version deleted]]
> >
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