# --------------------------------------
# Construct xts data.
# --------------------------------------

rows_to_build <- 6

dates <- seq(
  as.POSIXct("2019-01-01 09:01:00"),
  length.out = rows_to_build,
  by = "1 min",
  tz = "CEST"
  )

master_decision = c(
            # - Clarification what "for-loop" should do:
    3,      # Keep (missing [3] above)
    2,      # Keep (missing [2] above)
    2,      # Delete due to [2] on line above.
    3,      # Keep (missing [3] above)
    3,      # Delete due to [3] on line above.
    2       # Keep (missing [2] above)
)

data <- data.frame(master_decision)
xts1 <- xts(x = data, order.by = dates)


rm(list = ls()[! ls() %in% c("xts1")]) # Only keep [xts1].


# ------------------------------------------------------------
# For loop with purpose to remove duplicates that are grouped.
# ------------------------------------------------------------

for (i in 2:nrow(xts1)) {
    if(xts1[[i]] == xts1[[i-1]]) {
        xts1[-c(i)]
    }
}

master_decision
2019-01-01 09:01:00               3
2019-01-01 09:02:00               2
2019-01-01 09:03:00               2
2019-01-01 09:04:00               3
2019-01-01 09:05:00               3
2019-01-01 09:06:00               2

master_decision
2019-01-01 09:01:00               3
2019-01-01 09:02:00               2
2019-01-01 09:03:00               2
2019-01-01 09:04:00               3
2019-01-01 09:06:00               2

2019-01-01 09:01:00               3
2019-01-01 09:02:00               2
2019-01-01 09:04:00               3
2019-01-01 09:06:00               2