Using R to recode several variable at once

Question

My data set is like the following:

Q_B      Q1      Q2      Q3       Q4
1         5       4       5       3
2  
1         3       4       3       1
2                                  
1         1       1       1       1

What I'm doing is to change Q1 to Q4 to 0 if Q_B==2, I use Q1[Q_B==2]<-0,Q2[Q_B==2]<0

I have to write the same code for Q1 to Q4, is there a easy way to do that? Thanks!

Answer 1

We can just do

df1[df1$Q_B==2,-1] <- 0

data

df1 <- structure(list(Q_B = c(1L, 2L, 1L, 2L, 1L), Q1 = c(5L, NA, 3L, 
NA, 1L), Q2 = c(4L, NA, 4L, NA, 1L), Q3 = c(5L, NA, 3L, NA, 1L
), Q4 = c(3L, NA, 1L, NA, 1L)), .Names = c("Q_B", "Q1", "Q2", 
"Q3", "Q4"), class = "data.frame", row.names = c(NA, -5L))