Split periods into monthly intervals

Splits rows where the time period is longer than one month into multiple rows with a time period of exactly one month each. Values in numeric columns (e.g. exposure or premium) are divided proportionally over the months.

This function uses standard evaluation (SE): column names must be passed as character strings (e.g. begin = "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, begin, end, cols = NULL)

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

Arguments

df

A data.frame or data.table.

begin

Character string. Name of column in df with begin dates.

end

Character string. Name of column in df with end dates.

cols

Character vector with names of numeric columns in df to split.

...

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

In insurance portfolios it is common that rows relate to periods longer than one month. This can be problematic when monthly exposures are needed.

Since insurance premiums are assumed constant over months (and not depending on the number of days per month), the function assumes each month has 30 days.

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,
  begin = "begin_date", end = "end_date",
  cols = c("premium", "exposure")
)
#>   id begin_date   end_date   exposure  premium id    new_end
#> 1  1 2014-01-01 2014-01-31 0.08209459 50.67568  1 2014-03-15
#> 2  1 2014-02-01 2014-02-28 0.08209459 50.67568  1 2014-03-15
#> 3  1 2014-03-01 2014-03-31 0.03831081 23.64865  1 2014-03-15
#> 4  2 2014-01-01 2014-01-31 0.08268462 34.61538  2 2014-05-11
#> 5  2 2014-02-01 2014-02-28 0.08268462 34.61538  2 2014-05-11
#> 6  2 2014-03-01 2014-03-31 0.08268462 34.61538  2 2014-05-11
#> 7  2 2014-04-01 2014-04-30 0.08268462 34.61538  2 2014-05-11
#> 8  2 2014-05-01 2014-05-31 0.02756154 11.53846  2 2014-05-11

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