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

No one seems to have included the which function. It can also prove useful for filtering.

expr[which(expr$cell == 'hesc'),]

This will also handle NAs and drop them from the resulting dataframe.

Running this on a 9840 by 24 dataframe 50000 times, it seems like the which method has a 60% faster run time than the %in% method.