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Force Legends to Merge

Source: R/legend_multi.R
legend_merge.Rd

Force specified legends to merge together by setting them to the same order. Legends will only merge if they have matching labels (same factor levels or break values).

Usage

legend_merge(...)

Arguments

...

Aesthetic names (unquoted) to merge. E.g., colour, fill.

Value

A guides specification that can be added to a plot.

Details

ggplot2 automatically merges legends when they have the same title and matching labels. This function ensures legends have the same order value (order = 0), which is a prerequisite for merging.

If legends still don't merge after using this function, ensure:

  • Both aesthetics map to the same variable

  • The legends have identical titles (use labs())

  • The breaks/labels are identical

See also

legend_split, legend_order_guides

Examples

library(ggplot2)

# Plot where colour and fill map to the same variable
p <- ggplot(mtcars, aes(mpg, wt, color = factor(cyl), fill = factor(cyl))) +
  geom_point(shape = 21, size = 3, stroke = 1.5) +
  labs(color = "Cylinders", fill = "Cylinders")

# Force merge (they should merge automatically if labels match)
p + legend_merge(colour, fill)