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Place Legend on the Left with Proper Alignment

Source: R/legend_position.R
legend_left.Rd

A one-liner to position the legend on the left side of the plot. Slides the legend along the left rail via justification, and left-aligns multiple legend boxes via legend.box.just.

Usage

legend_left(justification = "center", by = NULL)

Arguments

justification

Where the legend sits along the left edge. One of "top", "center", "bottom", or a numeric value in [0, 1] (0 = bottom, 1 = top). Default is "center". Only used when by is NULL. For per-guide justification, use legend_style(by = ..., justification = ...).

by

Optional aesthetic name (character) to position only a specific legend. When specified, uses per-guide positioning via guide_legend(position = "left"). Requires ggplot2 >= 3.5.0. Common values: "colour", "fill", "size".

Value

A ggplot2 theme object (when by is NULL) or a guides specification (when by is specified).

Details

The left-positioned legend lives in a vertical rail along the panel's left edge. justification slides it along that rail: "top" pins the legend's top edge to the panel top; "bottom" pins its bottom edge to the panel bottom; "center" centers it vertically.

Note the naming asymmetry with legend_inside: for side legends the justification keyword refers to where the legend sits along the panel edge; for inside legends it refers to which corner of the legend anchors to the (x, y) position.

When by is NULL (default), this function sets:

  • legend.position = "left"

  • legend.justification.left = justification

  • legend.box.just = "left" to left-align multiple legend boxes

When by is specified, only the legend for that aesthetic is moved.

See also

legend_right, legend_top, legend_bottom, legend_inside, legend_none

Examples

library(ggplot2)

# Basic usage — legend centered vertically on the left
ggplot(mtcars, aes(mpg, wt, color = factor(cyl))) +
  geom_point() +
  legend_left()

# Pin legend to the top of the left rail
ggplot(mtcars, aes(mpg, wt, color = factor(cyl))) +
  geom_point() +
  legend_left(justification = "top")

# Position only the colour legend on the left
ggplot(mtcars, aes(mpg, wt, color = factor(cyl), size = hp)) +
  geom_point() +
  legend_left(by = "colour") +
  legend_bottom(by = "size")