the default value of ScaleBinned$n.breaks should be 4, not 5.

[microly]

The default value of ScaleBinned$n.breaks was set to the same as trans objects.
The default value of trans objects can map data to 5 colours in plot and legend, which is a direct-viewing color display.

However, when n.breaks is set to 5, ScaleBinned will map the data to 6 colours!
6 colours display is not so good as 5 colours.

This occur in the codes:

ggplot2/R/scale-.r

Line 914 in 115c396

breaks <- sort(unique(c(limits[1], breaks, limits[2])))

and

ggplot2/R/scale-.r

Line 928 in 115c396

pal <- self$palette(breaks[-1] - diff(breaks) / 2)

So I think the default value of ScaleBinned$n.breaks should be 4, not 5, then it can works the same way as trans objects.

@thomasp85 , please consider it, thanks!

[clauswilke]

Could you provide a reprex that demonstrates the problem with the current code base?

[microly]

@clauswilke
Sure!

I have not used reprex before.
I will learn it and provide a demonstration soon.

[microly]

@clauswilke
I try to use the reprex package.
However, because of the government regulation of Internet, I cannot connect to "imgur.com" from the mainland of China.
So I have to supply graphic examples by hand.

[batpigandme]

Ah @microly, the GFW issue with reprex/imgur is unfortunate, and known.
tidyverse/reprex#220 (comment)
In lieu of running an actual reprex, could you give the full code for your example so one of us could run it locally?

There is an open issue in reprex in hopes of resolving this one day: tidyverse/reprex#214

[microly]

Here are the examples:

By now, The default value of ScaleBinned$n.breaks is 5.

Scale_fill_fermenter (which based on ScaleBinned) has six colours in the legend, which is different from scale_fill_distiller (which based on ScaleContinuous).

After setting ScaleBinned$n.breaks to 4, it works the same way like scale_fill_distiller, both of which have 4 colours in their legends.

library(ggplot2)
library(tibble)

ggplot(tibble(x = 1:10, y = x, z = x), aes(x, y, fill = z)) +
    geom_point(shape = 21, size = 10) +
    scale_fill_fermenter(trans = "identity", nice.breaks = F,
                         n.breaks = 5,
                         guide = "legend")

ggplot(tibble(x = 1:10, y = x, z = x), aes(x, y, fill = z)) +
    geom_point(shape = 21, size = 10) +
    scale_fill_fermenter(trans = "identity", nice.breaks = F,
                         n.breaks = 4,
                         guide = "legend")

ggplot(tibble(x = 1:10, y = x, z = x), aes(x, y, fill = z)) +
    geom_point(shape = 21, size = 10) +
    scale_fill_distiller(trans = "identity",
                         guide = "legend")

[microly]

@batpigandme
Thanks for your kind reply!
I past the example codes above.
I think it can be saw now.

[thomasp85]

We are pending an update to the scales package before we can actually pass n.breaks forward. The current values are not expected to make it to the release, but we will wait to change it until it has an effect

[microly]

OK, thanks for your reply~

[thomasp85]

I am closing this. The default of 5 makes sense as you'd generally want a break in the middle of your range instead of having a bin that spans over the middle. You shouldn't use the legend guide with a binned scale as it does not communicate the actually scale. Use the 'bins' guide instead