I'd like to post an Excel file to ask the community how I can replicate the results. Any suggestions on how I can upload an excel file? In the meantime, the picture illustrates what I am trying to replicate in R (i.e., the grey boxed area is what I am trying to recreate in R. (It's a vintage analysis with dummy data!)

```
dat <- structure(list(Vintage = c(201912L, 201912L, 201912L, 202001L,
202001L, 202002L), Month_Key = c(201912L, 202001L, 202002L, 202001L,
202002L, 202002L), MOB = c(0L, 1L, 2L, 0L, 1L, 0L), Units = c(21684L,
21277L, 20216L, 10559L, 10340L, 9952L), Model_UPB = c(1e+06,
941544.3761, 870733.2831, 1e+06, 939308.4539, 1e+06), Model_NCO = c(1000,
12785.51286, 48072.55081, 1000, 9721.796368, 1000), Actual_UPB = c(1e+06,
933959.488, 892096.5154, 1e+06, 929145.0864, 1e+06), Actual_NCO = c(250,
68824.8, 70067.32, 250, 16714.96, 250)), class = "data.frame", row.names = c(NA,
-6L))
dat
```