# [R] graphical behavior of a table of numbers

Richard M. Heiberger rmh at temple.edu
Mon Jan 30 16:19:53 CET 2017

```Duncan, thank you for locating the problem.
Martin, thank you for explaining the behavior and for the first pass
at fixing it.
With the fix, now the x-axis has ticks at all integers, and tick labels at
c(-81,-67,-53,-39,-25,-11,0,9,19,31,43,55,67,79)
This is with R-3.3.2, as I interpret your fix to be to only the
R-intro.pdf manual with no change
to the code of any of the functions.
More work has to be done to repair the example.

I recommend
plot(as.numeric(fr) ~ as.numeric(names(fr)), type="h",
xlab="Determinant", ylab="Frequency")

The slightly more obvious solution doesn't work
> plot(fr ~ as.numeric(names(fr)), type="h", xlab="Determinant", ylab="Frequency")
Error in plot.table(c(-81, -80, -79, -78, -77, -76, -75, -74, -73, -72,  :
invalid table 'x'

## It is possible to change graphics:::Axis.table to
if (is.num) axis(side, ...)
## and that would make the x-axis for the determinant example
plot(fr, type="h", xlab="Determinant", ylab="Frequency")
## look sensible, but would
## be less appropriate for the following example.

## The current behavior of Axis.table makes sense in this example
tt <- as.table(array(c(10,20,30), dimnames=list(c(100, 120, 200))))
tt
plot(tt)

On Mon, Jan 30, 2017 at 5:38 AM, Martin Maechler
<maechler at stat.math.ethz.ch> wrote:
>>>>>> Duncan Murdoch <murdoch.duncan at gmail.com>
>>>>>>     on Sun, 29 Jan 2017 06:32:27 -0500 writes:
>
>     > On 29/01/2017 12:05 AM, Jim Lemon wrote:
>     >> Hi Richard, I think there may be something amiss in the
>     >> plot.table function. As you note, changing the class of
>     >> fr to array produces a more sensible plot, as does Bert's
>     >> "as.vector". Yet inside plot.table we find:
>     >>
>     >> plot(x0, unclass(x), ...
>     >>
>     >> and that should produce an array:
>     >>
>     >> class(unclass(fr)) [1] "array"
>     >>
>     >> The plot.table function looks like it should produce the
>     >> plot you want, but it doesn't. I think (therefore I am
>     >> probably wrong) that a 1D table is handled in the same
>     >> way as multiD table rather than being squeezed into a
>     >> vector.
>
>     > I think the issue is that Axis() is called without
>     > removing the class.  Axis.table sets ticks based on the
>     > names of the table.
>
>     > Duncan Murdoch
>
> yes indeed!  So this answers Rich Heiberger's question.
>
> The example stems from a time long before there was
> a plot.table() method, and even longer before plot.default() had
> started using  Axis() and its methods.
>
> So a much nicer example for the R-intro -- committed a few
> minutes ago -- is making use of the  plot.table() S3 method :
>
>   d <- outer(0:9, 0:9)
>   fr <- table(outer(d, d, "-"))
>   plot(fr, type="h", xlab="Determinant", ylab="Frequency")
>
> So this fulfills Rich's recommendation.
>
> Martin
>
>
>     >> On Sun, Jan 29, 2017 at 11:19 AM, Bert Gunter <bgunter.4567 at gmail.com> wrote:
>     >>> Rich:
>     >>>
>     >>> Simpler: Just lose the "table" class.
>     >>>
>     >>> plot(as.numeric(names(fr)), as.vector(fr),  type="h",
>     >>>      xlab="Determinant", ylab="Frequency")
>     >>>
>     >>> However, I'm no less puzzled by the "strange" behavior than you.
>     >>>
>     >>> In addition, it's probably worth noting that xyplot in lattice (and no
>     >>> doubt ggplot,too) does not have this problem (as I'm sure you know):
>     >>>
>     >>> xyplot(fr ~ as.numeric(names(fr)),  type="h",
>     >>>        xlab="Determinant", ylab="Frequency")
>     >>>
>     >>>
>     >>> Cheers,
>     >>> Bert
>     >>> Bert Gunter
>     >>>
>     >>> "The trouble with having an open mind is that people keep coming along
>     >>> and sticking things into it."
>     >>> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>     >>>
>     >>>
>     >>> On Sat, Jan 28, 2017 at 3:03 PM, Richard M. Heiberger <rmh at temple.edu> wrote:
>     >>>> ## This example is from R-intro.pdf page 21 (R-3.3.2)
>     >>>>
>     >>>> d <- outer(0:9, 0:9)
>     >>>> fr <- table(outer(d, d, "-"))
>     >>>> plot(as.numeric(names(fr)), fr, type="h",
>     >>>>      xlab="Determinant", ylab="Frequency")
>     >>>> ## The y-axis tick marks are at c(-21,24,65).
>     >>>> ## This seems to be because class(fr) == "table"
>     >>>>
>     >>>> ## Switching the class to array gives the more appropriate
>     >>>> ## y-axis ticks at seq(0,500,100) .
>     >>>>
>     >>>> fr.array <- fr
>     >>>> class(fr.array) <- "array"
>     >>>> plot(as.numeric(names(fr)), fr.array, type="h",
>     >>>>      xlab="Determinant", ylab="Frequency")
>     >>>>
>     >>>>
>     >>>> ## I have a question and a recommendation.
>     >>>> ## Question:
>     >>>> ## Why are the y-axis ticks for the table defaulted to c(-21,24,65).
>     >>>> ##
>     >>>> ## Recommendation:
>     >>>> ## Changed the example on page 21 to show the ticks at seq(0,500,100)?
>     >>>>
>     >>>> ## Rich
>     >>>>
>
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