labeled breaks for binned color scale malfunction when show.limits = T

[waynerroper]

---

When formatting labels for breaks in color scales, ggplot returns an error for the length of label vector if show.limits = T. This error appears even if the breaks and labels vectors are the same length.

This may be because limits and breaks are passed to different vectors before compiling the final plot and therefore the user cannot easily write labels for limits and breaks together. An example is provided here: https://stackoverflow.com/questions/71976832/custom-labels-for-limit-and-break-values-when-using-scale-color-binned-in-r-ggpl

Is it possible to integrate limits and breaks in a more streamlined way to avoid the error message and not have to define labels with a custom function that circumvents the issue?

library(ggplot2)

ggplot(mpg, aes(cty, hwy, color = year)) +
  geom_point() +
  scale_color_binned(limits = c(1999, 2008),
                    breaks = c(2000, 2002, 2004, 2006),
                    labels = c('2', '3', '4', '5'),
                    show.limits = F) # labels work

ggplot(mpg, aes(cty, hwy, color = year)) +
  geom_point() +
  scale_color_binned(limits = c(1999, 2008),
                    breaks = c(2000, 2002, 2004, 2006),
                    labels = c('2', '3', '4', '5'),
                    show.limits = T) # method fails when limits are activated

    # Error in f(): ! Breaks and labels are different lengths

[yutannihilation]

Thanks, confirmed. It seems the problem is that, when show.limits = TRUE, the labels for the upper and lower limits are set separately with scale$get_labels(), whereas get_labels() always validates the result against the supplied labels.

ggplot2/R/guide-colorsteps.R

Lines 104 to 110 in b9e1694

	if (guide$show.limits %||% scale$show.limits %||% FALSE) {
	edges <- rescale(c(0, 1), to = guide$bar$value[c(1, nrow(guide$bar))], from = c(0.5, guide$nbin - 0.5) / guide$nbin)
	if (guide$reverse) edges <- rev(edges)
	guide$key <- guide$key[c(NA, seq_len(nrow(guide$key)), NA), , drop = FALSE]
	guide$key$.value[c(1, nrow(guide$key))] <- edges
	guide$key$.label[c(1, nrow(guide$key))] <- scale$get_labels(limits)
	}

ggplot2/R/scale-.r

Lines 1122 to 1135 in b9e1694

	if (is.null(self$labels)) {
	return(NULL)
	} else if (identical(self$labels, NA)) {
	abort("Invalid labels specification. Use NULL, not NA")
	} else if (is.waive(self$labels)) {
	labels <- self$trans$format(breaks)
	} else if (is.function(self$labels)) {
	labels <- self$labels(breaks)
	} else {
	labels <- self$labels
	}
	if (length(labels) != length(breaks)) {
	abort("Breaks and labels are different lengths")
	}