我怎样才能 select 仅从 R 中满足特定条件的数据框中的一列

Question

I am new to R and I am doing some exercises but I do not get the expected output. I created a data frame with 4 columns. ab,c,d I want to see in my output column c when column d only has values ( B and C) only.

The way I am doing is subset(DFAsg1, b == "B" | y == "C")

this returns all the columns in the data frame, but I want to select only column c.

Answer 1

subset(DFAsg1, b == "B" | y == "C", select = "c")

Answer 2

We could do

if(all(DFAsg1$d %in% c("B", "C"), na.rm = TRUE)) DFAsg1['c']