make_rnk: Make rank lists
In jacobheng/cellwrangler: Supplemental toolkit for single-cell RNAseq analysis

make_rnk() makes rank lists for pre-ranked geneset enrichment analysis.

1 2	make_rnk(celltype, rank_df, gene_name, rank_stat, decreasing = T, write_rnk = F, output_dir = NULL, output_name = NULL)

`celltype`	CellType to create rank lists for.
`rank_df`	a dataframe with the pre-requisite rank statistics
`gene_name`	column in rank_df containing gene names.
`rank_stat`	column in rank_df containing statistic to rank genes by.
`decreasing`	logical; whether to rank genes by decreasing value of rank_stat.
`write_rnk`	logical; whether to write .rnk files for GSEA
`output_dir`	name of directory to write .rnk files to; if directory does not exist, it will be created
`output_name`	prefix for .rnk file names; .rnk files will be named "output_name_celltype.rnk"
`group_column`	column name of column in annotation object with values corresponding to those in group_vector to use for computing logical columns. Defaults to NULL