White Big White Big - 17 days ago 5
R Question

add column based on values in other columns data frame r

I'm curious about how to solve this problem. I have data frame like this:

a b
1 0
1 0
0 1
1 1
0 0
1 0


Then the output has an extra column based on values of "a" and "b":

if(a==1&b==1) c=1, if(a==1&b==0) c=2, if(a==0&b==1) c=3, else c=4.

a b c
1 0 2
1 0 2
0 1 3
1 1 1
0 0 4
1 0 2


Any thoughts? I don't to write a for loop with nested if-else, how could we go vectorize? Thanks!

Answer

interaction is made for this:

c(4,2,3,1)[interaction(df)]
#[1] 2 2 3 1 4 2
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