Generate truncated reporting triangles — truncate

This function ingests a reporting triangle/matrix and the number of truncated reporting triangles we want to create, n, and iteratively truncates the reporting triangle, working from the latest reference time (bottom) to the older reference times (top) for n snapshots.

Usage

truncate_triangles(
  reporting_triangle,
  n = nrow(reporting_triangle) - sum(is.na(rowSums(reporting_triangle))) - 1
)

Arguments

reporting_triangle: Matrix of the reporting triangle, with rows representing the time points of reference and columns representing the delays. Can be a reporting matrix or incomplete reporting matrix. Can also be a ragged reporting triangle, where multiple columns are reported for the same row. (e.g. weekly reporting of daily data).
n: Integer indicating the number of retrospective truncated triangles to be generated, always starting from the most recent reference time. Default is to generate truncated matrices for each row up until there are insufficient rows to generate nowcasts from, where the minimum requirement is one more than the number of horizon rows (rows containing NAs).

Value

trunc_rep_tri_list List of n truncated reporting triangle matrices with as many rows as available given the truncation, and the same number of columns as reporting_triangle.

Examples

triangle <- matrix(
  c(
    65, 46, 21, 7,
    70, 40, 20, 5,
    80, 50, 10, 10,
    100, 40, 31, 20,
    95, 45, 21, NA,
    82, 42, NA, NA,
    70, NA, NA, NA
  ),
  nrow = 7,
  byrow = TRUE
)

truncated_rts <- truncate_triangles(triangle, n = 2)
truncated_rts[1:2]
#> [[1]]
#>      [,1] [,2] [,3] [,4]
#> [1,]   65   46   21    7
#> [2,]   70   40   20    5
#> [3,]   80   50   10   10
#> [4,]  100   40   31   20
#> [5,]   95   45   21   NA
#> [6,]   82   42   NA   NA
#> 
#> [[2]]
#>      [,1] [,2] [,3] [,4]
#> [1,]   65   46   21    7
#> [2,]   70   40   20    5
#> [3,]   80   50   10   10
#> [4,]  100   40   31   20
#> [5,]   95   45   21   NA
#>