PriceIndices (version 0.0.7)

final_index: The most general package function to compute the price dynamics

Description

This function returns a value or values of the selected (final) price index taking into consideration aggregation over product subgroups and/or over outlets.

Usage

final_index(
  datasets = list(),
  start,
  end,
  formula = "fisher",
  window = 13,
  splice = "movement",
  base = start,
  sigma = 0.7,
  aggrret = "tornqvist",
  aggrsets = "tornqvist",
  interval = FALSE
)

Value

This function returns a value or values of the selected (final) price index taking into consideration aggregation over product subgroups and/or over outlets (retailer sale points defined in retID column) . To be more precise: if both types of aggregation are selected, then for each subgroup of products and for each outlet (point of sale) price indices are calculated separately and then aggregated (according to the aggregation methods indicated) to the form of the final price index. If the interval parameter is set to TRUE then it returns a data frame with two columns: dates and final index values (after optional aggregating). Please note that different index formulas may use different time intervals (or time periods) for calculations and each time, aggregation over outlets is done for the set of retIDs being available during the whole considered time interval.

Arguments

datasets

The user's list of data frames with subgroups of sold products. Each data frame must contain columns: time (as Date in format: year-month-day,e.g. '2020-12-01'), prices (as positive numeric), quantities (as positive numeric), prodID (as numeric, factor or character) and retID (as numeric, factor or character).

start

The base period (as character) limited to the year and month, e.g. "2019-12".

end

The research period (as character) limited to the year and month, e.g. "2020-04".

formula

The character string indicating the (final or main) price index formula is to be calculated. To see available options please use the link: PriceIndices.

window

The length of the time window if the multilateral index is selected (as positive integer: typically multilateral methods are based on the 13-month time window and thus the default value is 13).

splice

A character string indicating the splicing method (if the multilateral splicing index is selected). Available options are: "movement", "window","half", "mean" and also "window_published", "half_published" and "mean_published".

base

The prior period used in the Young- or Lowe-type price indices (as character) limited to the year and month, e.g. "2020-01".

sigma

The elasticity of substitution parameter used in the Lloyed-Moulton and AG Mean indices (as numeric).

aggrret

A character string indicating the formula for aggregation over outlets (retailer sale points). Available options are: "none", "laspeyres", "paasche", "geolaspeyres", "geopaasche", "fisher", "tornqvist", "arithmetic" and "geometric". The first option means that there is no aggregating over outlets. The last two options mean unweighted methods of aggregating, i.e. the arithmetic or geometric mean is used.

aggrsets

A character string indicating the formula for aggregation over product subgroups. Available options are: "none", "laspeyres", "paasche", "geolaspeyres", "geopaasche", "fisher", "tornqvist", "arithmetic" and "geometric". The first option means that there is no aggregating over product subgroups. The last two options mean unweighted methods of aggregating, i.e. the arithmetic or geometric mean is used.

interval

A logical value indicating whether the function is to provide the price index comparing the research period defined by end to the base period defined by start (then interval is set to FALSE) or all fixed base indices are to be presented (the fixed base month is defined by start).

Examples

 final_index(datasets=list(milk),start="2018-12",end="2020-02",
formula="walsh",aggrret="paasche",aggrsets="none")
## defining two subgroups of milk
g1<-dplyr::filter(milk, milk$description=="full-fat milk UHT")
g2<-dplyr::filter(milk, milk$description=="low-fat milk UHT")
## Final price index calculations (for the whole time interval) 
## with aggregating over subgroups g1 and g2 and over outlets
## Please note that the default value (formula) for aggregating over outlets is "tornqvist""
final_index(datasets=list(g1,g2), start="2018-12",
end="2019-12",formula="fisher",aggrsets="geometric",interval=TRUE)