position_dodge() with order aesthetics for stacking and dodging

[alyst]

This plots as expected:

ggplot(mpg, aes(x = class, order = drv, fill = drv)) +
    geom_bar(position = position_dodge(preserve = "single")) +
    theme_bw()

This one is almost correct, but it seems the widths of the bars take into account the number of groups (5) rather then the number of distinct order values (3):

ggplot(mutate(mpg, drvXyear = paste0(drv, "|", year)),
       aes(x = class, order = drv, fill = drvXyear)) +
    geom_bar(position = position_dodge(preserve = "single")) +
    theme_bw()

ggplot2 v4.0.1

[teunbrand]

Thanks for the report! I agree there is some sense in deriving the width from the number of distinct values rather than groups. In the meanwhile you can also set the width manually.

[alyst]

I can set the width manually, but on the 2nd plot the bars are also offset to the left (the "f" barstack is centered on the first plot, but it is to the left of the center on the 2nd plot). With larger difference between the categories in the fill and the order aes it becomes even more apparent. Manually setting the width does not fix it. I think the position formula has to be fixed on the ggplot2 side.

[teunbrand]

on the 2nd plot the bars are also offset to the left (the "f" barstack is centered on the first plot, but it is to the left of the center on the 2nd plot).

Yes keeping the order consistent without re-centering is the exact purpose for which we conceived the order aesthetic, so I'd argue this is intended behaviour.

[alyst]

Yes keeping the order consistent without re-centering is the exact purpose for which we conceived the order aesthetic

I'm not sure I understand what you are saying. My point is that the offset from the center does not look like the intended behaviour.
Here's what happens when there are more groups -- the bars are shifted further to the left to the point that it's not clear to which X axis category they belong. And IIUC ggplot2 does not give users the control over this offset.

ggplot(mutate(mpg, drvXmodel = paste0(drv, "|", model)),
       aes(x = class, order = drv, fill = drvXmodel)) +
    geom_bar(position = position_dodge(preserve = "single")) +
    theme_bw()

Here's the same plot with width adjustment (both for aes and dodge -- setting just aes width makes the bars overlap).
I can tune the width to what I want, but the offset gets even worse.

ggplot(mutate(mpg, drvXmodel = paste0(drv, "|", model)),
       aes(x = class, order = drv, fill = drvXmodel)) +
    geom_bar(position = position_dodge(preserve = "single", width = 3.0), width = 3.0) +
    theme_bw()

[teunbrand]

My point is that the offset from the center does not look like the intended behaviour.

The intention is to have each bar with the same order value have the same distance from the group's center. It ensures that the order of bars across groups is consistent. In the very first plot you posted, this ensures that red is always left-of-center, green is at the center and blue is right-of-center, even if the group is incomplete. Sparser categories (first example of your previous post) also mean bigger gaps.

[alyst]

| The intention is to have each bar with the same order value have the same distance from the group's center

Yes, that's why I'm using it. And, considering all possible values of order, they should be centered around the group center. Which, i hope you agree, is not the case in the plots that i show.

[teunbrand]

I agree that they don't center in the plots you've shown, but I strongly disagree that they should be centered based on all possible values of order within an x-position.