[R-sig-teaching] Choice of graphics package

[Ista Zahn]

Woops, messed up the example! I meant

theme_set(theme_bw() +
          theme(rect = element_rect(fill = "gray10")))

scale_discrete <- scale_fill_manual(values = c("orange", "purple",
"pink", "cyan"))

ggplot(mtcars, aes(x = hp, fill = factor(gear))) + geom_bar()

i.e., the whole point is you don't need to add this stuff to every plot.

Best,
Ista

On Fri, Nov 27, 2015 at 9:13 PM, Ista Zahn <istazahn at gmail.com> wrote:
> Hi Randal,
>
> To be honest I don't know the lattice theme system at all, so it is
> entirely possible that you can easily do things there that are more
> complicated in ggplot2. However, it is easy to set theme and scale[1]
> defaults in ggplot2, e.g.,
>
> library(ggplot2)
>
> theme_set(theme_bw() +
>           theme(rect = element_rect(fill = "gray10")))
>
> scale_discrete <- scale_fill_manual(values = c("orange", "purple",
> "pink", "cyan"))
>
> ggplot(mtcars, aes(x = hp, fill = factor(gear))) + geom_bar() +
>   theme_bw() +
>   scale_fill_manual(values = c("orange", "purple", "pink", "cyan"))
>
>
> Best,
> Ista
>
> [1] In ggplot2 theme elements are distinct from scales, and AFAIK they
> have to be set separately.
>
> On Fri, Nov 27, 2015 at 6:24 PM, Randall Pruim <rpruim at calvin.edu> wrote:
>>
>> On Nov 27, 2015, at 3:37 PM, Ista Zahn <istazahn at gmail.com> wrote:
>>
>>> (Theming in ggplot2 generally requires you to do something to each plot,
>>> one of the downsides of ggplot2.)
>>
>> That is completely untrue. Whatever downsides ggplot2 may have, this is not
>> one of them.
>>
>>
>> Ista,
>>
>> My guess is that you didn’t understand my claim.  Either that or you know
>> something about ggplot2 that I’ve not been able to locate anywhere.  (Since
>> Hadley is on  this list, he can chime in if I’m missing something.)
>>
>> So let me explain what I mean with an example.
>>
>> Suppose I want to create six plots of various sorts.  Each of them uses
>> color according to a factor a with three levels.  That's groups = a in
>> lattice and colour = a in ggplot2.  So far so good.
>>
>> But after I have created all of these plots with the default color choices,
>> I decide I want to have the colors be blue, red, and 50% gray.  In lattice,
>> I can put this information into the default theme with
>>
>> trellis.par.set( superpose.symbol = list(col = c("blue", "red", "gray50")) )
>>
>> and without any adjustments to any of the plotting code, all the plots will
>> update to the new color scheme.   show.settings() will even show me what my
>> default theme looks like.
>>
>> One line of code changes in one place and all the plots are using the new
>> color scheme.  And if my new choices are choices I will use frequently, I
>> can put the theme into a package and do something like
>>
>> trellis.par.set(theme = theme.mosaic())
>>
>> There is also the option to add these themes to individual plots using the
>> par.settings argument — this is more like the ggplot2 way.
>>
>> In ggplot2, I need to add on scale_colour_manual() to EACH PLOT, or write
>> some sort of wrapper that does the job for me.  In either case, if I started
>> out using the defaults and want to make document-wide changes, I need to
>> edit EACH plot to get the desired affect.  In lattice, this is one line of
>> code and all the plots are good to go.
>>
>> Last I looked for this, ggplot2 did not provide a way to set these sorts of
>> defaults and generally prefers a system where all of this sort of theming is
>> located local to each plot.  So plots end up having a bunch of theme stuff
>> added on to them like
>>
>> + theme_minimal()
>> + scale_colour_manual(values = c(“blue”, “red”, “gray50”)
>> + etc.
>>
>> See the examples at
>>
>> http://docs.ggplot2.org/dev/vignettes/themes.html
>>
>> Especially for teaching, I find this to be a real problem.  I don’t want to
>> clutter up early examples with all this sort of formatting, but I do want to
>> control the choice of colors used so that they work well for printing or
>> projecting in my local environment.  When I’m producing a journal or some
>> other sort of report, this is less important because I generally don’t show
>> the code in the final document — only the plot.  But it still violates the
>> DRY principle (Don’t Repeat Yourself).
>>
>> —rjp
>>
>> PS.  I should have mentioned one commonly held, but poorly justified, reason
>> to prefer ggplot2 over lattice:  the default colors.  lattice makes it easy
>> to adjust the defaults.  latticeExtra even provides a ggplot2 look-alike
>> theme that will make your lattice plots look a lot like ggplot2 plots.  (The
>> won’t match exactly because they don’t include all of the same elements.
>> Liking elements available in one system but not in the other is a possible
>> reason to prefer one over the other.)  On the other hand, if you don’t like
>> the defaults in ggplot2 — you’re out of luck, you don’t get the change the
>> defaults.
>>
>>
>>
>>