Add highlighted regions to a Manhattan plot — highlight

Draws colored rectangular bands behind specified genomic regions. Useful for marking known GWAS loci, MHC region, or custom regions of interest.

Usage

highlight_regions(
  plt,
  regions,
  color = "#FFD700",
  alpha = 0.15,
  label_size = 2.5,
  label_y = "top",
  border = FALSE,
  border_color = "grey40"
)

Arguments

plt: A ggplot object from manhattan_plot() or similar.
regions: A data.frame with columns: chr (integer), start, end. Optional: label, color, alpha.
color: Default fill color for regions (if not specified per region).
alpha: Default transparency.
label_size: Font size for region labels.
label_y: Y-axis position for labels ("top" or numeric value).
border: If TRUE, draw a border around regions.
border_color: Border color.

Value

The ggplot object with region highlights added.

Examples

data(example_gwas)
plt <- manhattan_plot(example_gwas)
regions <- data.frame(
  chr = c(6, 1), start = c(25e6, 5e6), end = c(35e6, 20e6),
  label = c("MHC", "1p36")
)
highlight_regions(plt, regions)