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Split policy periods into monthly rows

Source: R/time_period_to_months.R
split_periods_to_months.Rd

Splits policy or exposure periods that cross calendar months into monthly rows. Numeric columns such as exposure or premium can be prorated over the resulting monthly rows.

This function uses standard evaluation (SE): column names must be passed as character strings (e.g. period_start = "begin_date"). The older function period_to_months() used non-standard evaluation (NSE) and is deprecated as of version 0.8.0.

Usage

split_periods_to_months(
  df,
  period_start = NULL,
  period_end = NULL,
  prorate_cols = NULL,
  begin = NULL,
  end = NULL,
  cols = NULL
)

period_to_months(df, begin, end, ...)

Arguments

df

A data.frame or data.table.

period_start

Character string. Name of the column with policy period start dates.

period_end

Character string. Name of the column with policy period end dates.

prorate_cols

Character vector with names of numeric columns to prorate over the monthly rows, for example exposure or premium.

begin, end, cols

Deprecated argument names kept for backward compatibility.

...

Columns in df to split. Deprecated, use cols instead.

Value

A data.frame with the same columns as in df, plus an id column.

Details

Rating and monitoring work often needs exposure, premium, claim counts, or policy counts by calendar month. Source portfolios, however, usually contain policy periods that start and end on arbitrary dates. This helper expands those periods into monthly rows before modelling, reporting, or joining to monthly portfolio summaries.

Prorated columns are distributed according to the part of the policy period that falls in each monthly row. Full months receive weight 1; partial months use a 30-day month convention. The total value of each prorated column is preserved per original row.

Author

Martin Haringa

Examples

library(lubridate)
portfolio <- data.frame(
  begin_date = ymd(c("2014-01-01", "2014-01-01")),
  end_date   = ymd(c("2014-03-14", "2014-05-10")),
  exposure   = c(0.2025, 0.3583),
  premium    = c(125, 150)
)

# New SE interface
split_periods_to_months(portfolio,
  period_start = "begin_date",
  period_end = "end_date",
  prorate_cols = c("premium", "exposure")
)
#>   id begin_date   end_date   exposure  premium
#> 1  1 2014-01-01 2014-01-31 0.08437500 52.08333
#> 2  1 2014-02-01 2014-02-28 0.07875000 48.61111
#> 3  1 2014-03-01 2014-03-14 0.03937500 24.30556
#> 4  2 2014-01-01 2014-01-31 0.08397656 35.15625
#> 5  2 2014-02-01 2014-02-28 0.07837813 32.81250
#> 6  2 2014-03-01 2014-03-31 0.08397656 35.15625
#> 7  2 2014-04-01 2014-04-30 0.08397656 35.15625
#> 8  2 2014-05-01 2014-05-10 0.02799219 11.71875

# Old NSE interface (deprecated)
if (FALSE) { # \dontrun{
period_to_months(portfolio, begin_date, end_date, premium, exposure)
} # }