use aes() and pass (or wrap) custom functions

[schloerke]

be able to pass functions directly to ggpairs

Ex:

data("tips", package = "reshape")
pm <- ggpairs(
  tips, 
  columns = 1:3, 
  mapping = ggplot2::aes(color = sex), 
  lower = list(
    combo = wrap("facethist", binwidth = 1),
    continuous = wrap(ggally_points, size = 5)
  )
)
pm

> str(pm)

Custom str.ggmatrix output: 
To view original object use 'str(pm, raw = TRUE)'

List of 13
 $ data       :'data.frame':    244 obs. of  7 variables:
  ..$ total_bill: num [1:244] 17 10.3 21 23.7 24.6 ...
  ..$ tip       : num [1:244] 1.01 1.66 3.5 3.31 3.61 4.71 2 3.12 1.96 3.23 ...
  ..$ sex       : Factor w/ 2 levels "Female","Male": 1 2 2 2 1 2 2 2 2 2 ...
  ..$ smoker    : Factor w/ 2 levels "No","Yes": 1 1 1 1 1 1 1 1 1 1 ...
  ..$ day       : Factor w/ 4 levels "Fri","Sat","Sun",..: 3 3 3 3 3 3 3 3 3 3 ...
  ..$ time      : Factor w/ 2 levels "Dinner","Lunch": 1 1 1 1 1 1 1 1 1 1 ...
  ..$ size      : int [1:244] 2 3 3 2 4 4 2 4 2 2 ...
 $ plots      :List of 9
  ..$ : chr "PM; aes: c(x = total_bill, colour = sex); fn: {wrap; fn: 'ggally_densityDiag'; with params: c()}; gg: FALSE"
  ..$ : chr "PM; aes: c(x = tip, y = total_bill, colour = sex); fn: {wrap; fn: 'ggally_cor'; with params: c()}; gg: FALSE"
  ..$ : chr "PM; aes: c(x = sex, y = total_bill, fill = sex); fn: {wrap; fn: 'ggally_box'; with params: c()}; gg: FALSE"
  ..$ : chr "PM; aes: c(x = total_bill, y = tip, colour = sex); fn: {wrap; fn: 'funcVal'; with params: c(size = 5)}; gg: FALSE"
  ..$ : chr "PM; aes: c(x = tip, colour = sex); fn: {wrap; fn: 'ggally_densityDiag'; with params: c()}; gg: FALSE"
  ..$ : chr "PM; aes: c(x = sex, y = tip, fill = sex); fn: {wrap; fn: 'ggally_box'; with params: c()}; gg: FALSE"
  ..$ : chr "PM; aes: c(x = total_bill, y = sex, fill = sex); fn: {wrap; fn: 'ggally_facethist'; with params: c(binwidth = 1)}; gg: FALSE"
  ..$ : chr "PM; aes: c(x = tip, y = sex, fill = sex); fn: {wrap; fn: 'ggally_facethist'; with params: c(binwidth = 1)}; gg: FALSE"
  ..$ : chr "PM; aes: c(x = sex, fill = sex); fn: {wrap; fn: 'ggally_barDiag'; with params: c()}; gg: FALSE"
 $ title      : chr ""
 $ verbose    : logi FALSE
 $ printInfo  : logi FALSE
 $ axisLabels : chr "show"
 $ xAxisLabels: chr [1:3] "total_bill" "tip" "sex"
 $ yAxisLabels: chr [1:3] "total_bill" "tip" "sex"
 $ legends    : logi FALSE
 $ gg         : NULL
 $ nrow       : int 3
 $ ncol       : int 3
 $ byrow      : logi TRUE
 - attr(*, "_class")= chr [1:2] "gg" "ggmatrix"```

[schloerke]

@briatte, can you take a look at this branch and mess around with ggpairs? I'd like to see if it's more fluid / non confusing.

I still have to reduce the parameters in the main ggally_(plot)s, but I'll do that tomorrow. corUse -> use

[briatte]

@schloerke I'm looking at the function's examples right now, after adapting them to a different dataset (the hdv2003 dataset in package questionr, which is a social survey with mostly ordinal/factor variables).

Here are two first impressions:

• you need a vignette

I believe that you really need a vignette for ggpairs – there's tons of great options, but few ways to discover them from the package.

In fact, as far as I understand, pretty much every major function of GGally requires a vignette. Perhaps this could be made a requirement for a function to be included in the package. Since graphics-based vignettes are heavy in size, I would recommend keeping them out of the package itself, and host them on GitHub instead.

• you need a "blank" default theme, and/or a theme argument

ggpairs uses theme_grey by default, but if you are emulating the pairs function, I believe it would make great sense to use theme_bw or something like that instead. In most of the examples that I ran, I found myself wanting the grey background (and panel grid) out, and axis labels to be more readable (i.e. printed in black instead of grey).

Adding a theme to ggpairs object does not propagate the theme to its components:

library(questionr)
data(hdv2003)
p = ggpairs(
  hdv2003[, 2:4 ],
  upper = list(continuous = "density", combo = "box"),
  lower = list(continuous = "points", combo = "dot")
)
p + theme_bw()

How about allowing this:

ggpairs(
  hdv2003[, 2:4 ],
  upper = list(continuous = "density", combo = "box"),
  lower = list(continuous = "points", combo = "dot"),
  theme = theme_bw()
)

What do you think?