Filter data.frame rows by a logical condition

Question

I want to filter rows from a data.frame based on a logical condition. Let\'s suppose that I have data frame like

   expr_value     cell_type
1           


        

Answer 1

To select rows according to one 'cell_type' (e.g. 'hesc'), use ==:

expr[expr$cell_type == "hesc", ]

To select rows according to two or more different 'cell_type', (e.g. either 'hesc' or 'bj fibroblast'), use %in%:

expr[expr$cell_type %in% c("hesc", "bj fibroblast"), ]