[R] lattice barchart() with two variables

[Bert Gunter]

No reproducible example (see posting guide below) so minimal help.

Remove the quotes from your formula. Why did you think they should be
there? -- see ?formula.

Read the relevant portions of ?xyplot carefully (again?). You seemed to
have missed:

"*Primary variables:* The x and y variables should both be numeric in xyplot,
and an attempt is made to coerce them if not. However, if either is a
factor, the levels of that factor are used as axis labels. In the other
four functions documented here, [ which includes barchart()]  **exactly one
of x and y should be numeric, and the other a factor or shingle**. Which of
these will happen is determined by the horizontal argument — if
horizontal=TRUE, then y will be coerced to be a factor or shingle, otherwise
 x. The default value of horizontal is FALSE if x is a factor or shingle,
TRUEotherwise. (The functionality provided by horizontal=FALSE is not
S-compatible.)

So with the default ... horizontal = FALSE, Med would be treated as a
factor, which I think is precisely the opposite of what you want.

Here is a simple example to indicate how things work:

y <- runif(5)
x <- factor(letters[1:5])
barchart(y~x)

As for fiddling with the colors and patterns of the bars -- generally a bad
idea , especially fill patterns, btw -- see the "col" argument of
?panel.barchart, which is always where you should look for such info (i.e.
panel.whatever). I don't know whether you can fool with fill patterns* --
it may depend on your graphics device -- but you can google around or see
what trellis.par.get() has available (which can be specified in the
"par.settings" argument list in the call).

* For why fooling with fill patterns is a bad idea, google "moiré patterns".

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 Wed, Aug 22, 2018 at 8:13 AM Rich Shepard <rshepard using appl-ecosys.com>
wrote:

>    I've not before created bar charts, only scatter plots and box plots.
> Checking in Deepayan's book, searching the web, and looking at ?barchart
> has
> not shown me the how to get the results I need.
>
>    The dataframe looks like this:
> > head(stage_heights)
>    Year   Med   Max
> 1 1989 91.17 93.32
> 2 1990 91.22 93.43
> 3 1991 91.24 92.89
> 4 1993 91.14 93.02
> 5 1994 93.92 95.74
> 6 1995 94.34 96.85
>
>    I want to show Med and Max heights for each Year with each bar having a
> different color (or pattern) and a single x-axis year label.
>
>    Trying to follow the example in ?barchart for a single variable
> produced this:
>
> > barchart('Year' ~ 'Med', data=stage_height,
> panel=lattice.getOption('panel.barchart'),
> default.prepanel=lattice.getOption('prepanel.default.barchart'),box.ratio=2)
> Error in eval(substitute(groups), data, environment(formula)) :
>    invalid 'envir' argument of type 'closure'
> and no plot was displayed.
>
>    I must be missing the obvious and want a pointer to descriptions that
> teach me how to produce bar charts.
>
> Rich
>
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