preventing fill for density plot in densigram marginal

[IndrajeetPatil]

Thank you so much for introducing the densigram! Really stoked about using it.

I was trying it out, but I feel like it is still missing something: In particular, it looks good only with the (black-and-white) defaults and loses its allure once fill arguments are provided.

For example,

# loading needed libraries
library(ggExtra)
library(ggplot2)
library(cowplot)

# preparing basic plot
set.seed(30)
df <- data.frame(x = rnorm(500, 50, 10), y = runif(500, 0, 50))
p2 <- ggplot(df, aes(x, y)) + geom_point()

# trying out densigram
cowplot::plot_grid(
# with default color fill
ggMarginal(p2, xparams = list(colour = "black"),
           yparams = list(colour = "black"), type = "densigram"),

# without default color fill
ggMarginal(p2, xparams = list(colour = "black", fill = "red"),
            yparams = list(colour = "black", fill = "blue"), type = "densigram"),
nrow = 1,
ncol = 2
)

To go back to the python example I had shown in my original issue (https://github.com/daattali/ggExtra/issues/118), this is the behavior I was expecting with densigram:

Here, the fill arguments are being supplied only to the histogram component, but not the density plot component. Is this something that will be possible to do in ggMarginal?

Thanks again!

[crew102]

I guess we could override the fill param to be NULL for the density plot when the user choses type = "densigram". That would result in the plot looking like the one you showed. I don't feel particularly strongly about it either way. If @daattali also doesn't have strong feelings about it then I'll add this behavior in.

More generally, I was thinking people would use the alpha param when using fill with densigrams:

library(ggExtra)

ggMarginal(
  data = mtcars, x = "mpg", y = "wt", type = "densigram", 
  colour = "blue", fill = "blue", alpha = .3
)

[daattali]

When I was checking it out I did indeed use alpha, but I suppose that does add an additional requirement on the user. It might be simpler to just remove the fill