How do I count the number of times where A happened and B happened with R from a table? -


let's data 

a b c 0 1 0 1 1 0   <- here , b 1 1 0 0 0 1 1 1 1 1   <- here 1 1 0   <- , here

i want count number of times both , b 1. in case 3. easy sql have no idea how r.

if df data.frame columns, a,b,c:

sum(df$a==1 & df$b==1)

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