lic_revenue: Calculate future license revenue streams by current age
In southwick-associates/lifetime: Provide functions for lifetime pricing

Description Usage Arguments Functions Examples

Calculate future license revenue streams by current age

lic_annual_stream(retain_all, prices)

lic_lifetime_stream(prices, return_life, inflation, fund_years = 0:500)

lic_lifetime(prices, return_life, inflation, fund_years = NULL,
  perpetuity = TRUE)

`retain_all`	data frame of predicted years by age like that produced by `nc_retain_all`
`prices`	data frame of lifetime prices by age with at least 2 variables: current_age and price_lifetime
`return_life`	percentage return from lifetime fund
`inflation`	inflation rate for depreciation of lifetime fund
`fund_years`	range of years to cast forward for stream-based lifetime fund valuation
`perpetuity`	if TRUE, use a perpetuity calculation (https://en.wikipedia.org/wiki/Perpetuity) instead of `present_value`

lic_annual_stream: Stream of Revenue for annual scenario (Revenue|A)
lic_lifetime_stream: Stream of Revenue for lifetime scenario (Revenue|L)
lic_lifetime: Total Revenue for lifetime scenario (Revenue|L)

library(dplyr)
library(ggplot2)
data(retain_all)

# annual revenue simply follows retention curves (assuming constant pricing)
prices <- tibble(current_age = 16:63, price_annual = rep(40, 48))
lic_annual_stream(retain_all, prices)

# stream of lifetime revenue
prices <- mutate(prices, price_lifetime = rep(250, 48))
lic_lifetime_stream(prices, 0.05, 0.0219)

# total lifetime revenue (perpetuity vs. 50-year ROI)
lic_lifetime(prices, 0.05, 0.0219)
lic_lifetime(prices, 0.05, 0.0219, fund_years = 0:50, perpetuity = FALSE)