How to remove row if it has a NA value in one certain column

The easiest solution is to use is.na():

df[!is.na(df$B), ]

which gives you:

   A B  C
1 NA 2 NA
2  1 2  3
4  1 2  3

there is an elegant solution if you use the tidyverse!

it contains the library tidyr that provides the method drop_na which is very intuitive to read.

So you just do:

library(tidyverse)

dat %>% drop_na("B")

OR

dat %>% drop_na(B)

if B is a column name