Add Simplified Axis Indicators to ggplot

Adds simplified axis indicators (arrows and labels) to a ggplot object, typically used for dimension reduction plots like UMAP or t-SNE.

theme_umap_arrows(
  anchor_x = unit(6, "mm"),
  anchor_y = unit(6, "mm"),
  line_length = unit(12, "mm"),
  arrow_length = unit(2.5, "mm"),
  text_offset_x = unit(2.5, "mm"),
  text_offset_y = unit(2.5, "mm"),
  text_size = 10,
  line_width = 1,
  x_label = NULL,
  y_label = NULL
)

Arguments

anchor_x

X-coordinate for the anchor point of the arrows, Default: unit(6, "mm")

anchor_y

Y-coordinate for the anchor point of the arrows, Default: unit(6, "mm")

line_length

Length of the arrow lines, Default: unit(12, "mm")

arrow_length

Length of the arrow heads, Default: unit(2.5, "mm")

text_offset_x

X-offset for the axis labels, Default: unit(2.5, "mm")

text_offset_y

Y-offset for the axis labels, Default: unit(2.5, "mm")

text_size

Font size for the axis labels, Default: 10

line_width

Width of the arrow lines, Default: 1

x_label

Custom label for the x-axis, Default: NULL (auto-detected)

y_label

Custom label for the y-axis, Default: NULL (auto-detected)

Value

A ggplot theme object that can be added to an existing ggplot

Details

This function creates a theme that adds simplified axis indicators to the bottom-left corner of a ggplot. It consists of two perpendicular arrows representing the x and y axes, along with their respective labels. This approach is particularly useful for dimension reduction plots like UMAP or t-SNE where traditional axes are often removed to reduce visual clutter. The function attempts to auto-detect axis labels, but custom labels can be provided.

Examples

library(Seurat)
library(SeuratExtend)

features <- c("cluster", "orig.ident", "CD3D", "CD14")

# Add arrows to the overall plot
DimPlot2(pbmc, features = features, theme = NoAxes()) +
  theme_umap_arrows()

# Add arrows to each subplot
DimPlot2(pbmc, features = features, theme = theme_umap_arrows())