looking up similarities between columns

I have a df like this.

df <- data.frame(
    b1 = c(2, 6, 3, 80, 4, 77, 1, 9, NA), 
    b2 = c(100, 3, 9, 102, 6, 12, 1, 7, 77))

I want to compare column b1 with column b2 for similarity. So if any number in b1 can be found in anywhere in b2 create a new column (new) and write YES.
The idea is to have something like this as my result.

df <- data.frame(
    b1 = c(2, 6, 3, 80, 4, 77, 1, 9, NA), 
    b2 = c(100, 3, 9, 102, 6, 12, 1, 7, 77),
    new = c('NO', 'YES', 'YES', 'NO', 'NO', 'YES', 'YES', 'YES', 'NO'))

I have tried unsuccessfully to work this out using this.

df$new <- ifelse(df$b1 == df$b2), YES, NO)

>Solution :

Use %in%:

df$b1 %in% df$b2
#[1] FALSE  TRUE  TRUE FALSE FALSE  TRUE  TRUE  TRUE FALSE

ifelse(df$b1 %in% df$b2, "YES", "NO")
#[1] "NO"  "YES" "YES" "NO"  "NO"  "YES" "YES" "YES" "NO"

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