Count the number of times that dulicate records appear in a dataframe

count-dupe-rows.R

x <- data.frame(
  col_a = c("A", "B", "A", "C", "A", "D", "B", "C"),
  col_b = c(1, 2, 1, 3, 9, 4, 2, 9)
)

x

#   col_a col_b
# 1     A     1
# 2     B     2
# 3     A     1
# 4     C     3
# 5     A     9
# 6     D     4
# 7     B     2
# 8     C     9

y <- aggregate(x, by = x, length)[-(ncol(x) + 1)]
names(y)[ncol(y)] <- "frequency"

y

#   col_a col_b frequency
# 1     A     1         2
# 2     B     2         2
# 3     C     3         1
# 4     D     4         1
# 5     A     9         1
# 6     C     9         1