Thanks @nirgrahamuk !
In this case, we are not forecasting, but we are just trying to add some figures manually for next few months based on growth%. So, for following sample data, I am looking to extend the data for 2024 Year by month with empty Sales at the moment which we will fill manually.
df <-
data.frame(
stringsAsFactors = FALSE,
Date = c("2023-01-01","2023-01-01",
"2023-01-01","2023-01-01","2023-02-01","2023-02-01",
"2023-02-01","2023-02-01","2023-03-01","2023-03-01",
"2023-03-01","2023-03-01","2023-04-01","2023-04-01",
"2023-04-01","2023-04-01","2023-05-01","2023-05-01",
"2023-05-01","2023-05-01","2023-06-01","2023-06-01",
"2023-06-01","2023-06-01","2023-07-01","2023-07-01",
"2023-07-01","2023-07-01","2023-08-01","2023-08-01",
"2023-08-01","2023-08-01","2023-09-01","2023-09-01",
"2023-09-01","2023-09-01","2023-10-01","2023-10-01","2023-10-01",
"2023-10-01","2023-11-01","2023-11-01","2023-11-01",
"2023-11-01","2023-12-01","2023-12-01","2023-12-01",
"2023-12-01","2023-12-01"),
Country = c("CA","CA","US","US","CA",
"CA","US","US","CA","CA","US","US","CA","CA","US",
"US","CA","CA","US","US","CA","CA","US","US",
"CA","CA","US","US","CA","CA","US","US","CA","CA",
"US","US","CA","CA","US","US","CA","CA","US",
"US","CA","CA","US","US","US"),
Type = c("A","B","A","B","A","B",
"A","B","A","B","A","B","A","B","A","B","A","B",
"A","B","A","B","A","B","A","B","A","B","A",
"B","A","B","A","B","A","B","A","B","A","B",
"A","B","A","B","A","B","A","B","B"),
Sales = c(460,470,480,490,500,510,
520,530,540,550,560,570,460,470,480,490,500,510,
520,530,540,550,560,570,60,470,480,490,500,
510,520,530,540,550,560,570,460,470,480,490,500,
510,520,530,540,550,560,570,-2)
)