Display legend for categorical data

The rscatter function has an argument showLegend to create a legend if using colorBy with a categorical data type. Below we plot the UMAP of 1.1M cells from the Tabula Sapiens dataset and color the points by cell type.

library(rscatter)
input <- if (file.exists("tabula_sapiens.parquet")) {
  "tabula_sapiens.parquet"
} else {
  "https://davidpross.com/tabula_sapiens.parquet"
}
cells <- arrow::read_parquet(input)
labels <- readLines("cell_type_mapping.csv")
rscatter(
  cells$umap1,
  cells$umap2,
  colorBy = factor(cells$cell_type, labels = labels),
  showLegend = TRUE
)

The legend above has interactivity where you can hover above a label to select points with that cell type and click the label to “lock” the selection.