R help - May 2020 - possible issue with scatterplot function in car package

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 at
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]]
> 
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

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 at 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 at
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]]
> >
> > ______________________________________________
> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
>
>
	[[alternative HTML version deleted]]

Dear Yousri,

The problem with scatterplot() is now fixed in the development version 3.0-8 of
the car package on R-Forge, which eventually will be submitted to CRAN. Until
then, you can install the package via install.packages("car",
repos="http://R-Forge.R-project.org")

Thanks again for the bug report,
 John
> On May 3, 2020, at 4:37 AM, Yousri Fanous <yousri.fanous at
gmail.com> wrote:
> 
> 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 at 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 at
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]]
> > 
> > ______________________________________________
> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
>