average_by_group: Average the expression matrix of Seurat by category
In Yutong441/TBdev: Infer a Trophoblast Developmental Trajectory

Average the expression matrix of Seurat by category

average_by_group(
  x,
  group.by,
  color_row,
  select_cells = NULL,
  slot_data = "data",
  assay = "RNA"
)

`x`	a Seurat object
`group.by`	a vector whose first item is the feature on which averaging is performed. Only the first item will be used in averaging. If a second item is supplied, then a metadata field will appear containing the most frequent item in the second category among the first category.
`select_cells`	on which subset of cells averaging is performed