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Specify treatment market shares for a budget impact model

Source: R/bim_market_share.R
bim_market_share.Rd

Defines how treatment market shares evolve over time, both in the current scenario (without the new drug) and in the new scenario (with the new drug introduced). Supports constant, linear ramp, logistic S-curve, and step uptake dynamics.

Usage

bim_market_share(
  population,
  treatments,
  new_drug,
  shares_current,
  shares_new,
  dynamics = c("constant", "linear", "logistic", "step"),
  uptake_params = NULL,
  scenarios = NULL
)

Arguments

population

A bim_population object from bim_population().

treatments

character. Vector of all treatment names, including the new drug.

new_drug

character(1). Name of the new intervention. Must be an element of treatments.

shares_current

Named numeric vector. Market shares in the current scenario (without the new drug). Values must sum to 1 and all be in [0, 1]. Names must match treatments.

shares_new

Named numeric vector. Market shares in the new scenario (with the new drug at full uptake). Values must sum to 1. Names must match treatments.

dynamics

character(1). How the new drug's uptake evolves:

  • "constant" – shares_new apply uniformly in all years (default).

  • "linear" – new drug ramps linearly from 0 to target share over uptake_params$ramp_years years.

  • "logistic" – S-curve uptake. Requires uptake_params$year_50pct and optionally uptake_params$steepness.

  • "step" – shares_new is a named list with one vector per year.

uptake_params

list or NULL. Parameters controlling uptake dynamics:

  • For "linear": list(ramp_years = 3).

  • For "logistic": list(year_50pct = 2, steepness = 2).

scenarios

Named list or NULL. Alternative market share vectors (named numerics, same structure as shares_new) for scenario analysis. E.g. list(conservative = c(...), optimistic = c(...)).

Value

An object of class bim_market_share, a list containing:

shares

A data.frame with columns year, treatment, scenario, share, n_patients.

params

List of input parameters.

meta

List with treatments, new_drug, dynamics.

See also

bim_population(), bim_model()

Examples

pop <- bim_population(
  indication  = "Disease X",
  country     = "GB",
  years       = 1:5,
  prevalence  = 0.003,
  n_total_pop = 42e6,
  eligible_rate = 0.30
)

ms <- bim_market_share(
  population     = pop,
  treatments     = c("RASi", "Sparsentan", "Sibeprenlimab"),
  new_drug       = "Sibeprenlimab",
  shares_current = c(RASi = 0.75, Sparsentan = 0.25, Sibeprenlimab = 0.00),
  shares_new     = c(RASi = 0.60, Sparsentan = 0.20, Sibeprenlimab = 0.20),
  dynamics       = "linear",
  uptake_params  = list(ramp_years = 3)
)
print(ms)
#> 
#> -- htaBIM Market Share --
#> 
#> Treatments : RASi, Sparsentan, Sibeprenlimab 
#> New drug   : Sibeprenlimab 
#> Dynamics   : linear 
#> Scenarios  : current, base 
#> 
#> Year 1 shares (base, with new drug):
#>   RASi                      : 70.0%
#>   Sparsentan                : 23.3%
#>   Sibeprenlimab             : 6.7%