Here is one way to do what you want.
DF <- data.frame(V1 = sample(c("A", "B"), 10, replace = TRUE),
V2 = sample(c("A", "B"), 10, replace = TRUE),
V3 = sample(c("A", "B"), 10, replace = TRUE),
V4 = sample(c("A", "B"), 10, replace = TRUE),
V5 = sample(c("A", "B"), 10, replace = TRUE),
V6 = sample(c("A", "B"), 10, replace = TRUE),
V7 = sample(c("A", "B"), 10, replace = TRUE),
V8 = sample(c("A", "B"), 10, replace = TRUE),
V9 = sample(c("A", "B"), 10, replace = TRUE), stringsAsFactors = FALSE)
DF
#> V1 V2 V3 V4 V5 V6 V7 V8 V9
#> 1 B A A B A A A B B
#> 2 A A B A A A A A A
#> 3 A B A A B B B A B
#> 4 A B A A A A A A A
#> 5 A A B B A A A B A
#> 6 A B A B A B A B A
#> 7 B B A B A A B B B
#> 8 A B B A B B A B A
#> 9 A A B A A B B B B
#> 10 B B B B A A A B B
COUNT_A <- function(row) {
if(sum(row == "A") >= sum(row == "B")) {
tmp <- "A"
} else {
tmp <- "B"
}
tmp
}
NewCol <- apply(DF, MARGIN = 1, FUN = COUNT_A)
DF$NewColumn <- NewCol
DF
#> V1 V2 V3 V4 V5 V6 V7 V8 V9 NewColumn
#> 1 B A A B A A A B B A
#> 2 A A B A A A A A A A
#> 3 A B A A B B B A B B
#> 4 A B A A A A A A A A
#> 5 A A B B A A A B A A
#> 6 A B A B A B A B A A
#> 7 B B A B A A B B B B
#> 8 A B B A B B A B A B
#> 9 A A B A A B B B B B
#> 10 B B B B A A A B B B
Created on 2020-05-03 by the reprex package (v0.3.0)