montgomery {PriceIndices}

Calculating the Montgomery price and quantity indicators

Description

This function returns the Montgomery price and quantity indicators and optionally also the price and quantity contributions of individual products.

Usage

montgomery(
  data,
  start,
  end,
  interval = FALSE,
  matched = FALSE,
  contributions = FALSE,
  prec = 2
)

Arguments

data

The user's data frame with information about sold products. It must contain columns: time (as Date in format: year-month-day,e.g. '2020-12-01'), prices (as positive numeric) and prodID (as numeric, factor or character). A column quantities (as positive numeric) is also needed because this function uses unit values as monthly prices.

start

The base period (as character) limited to the year and month, e.g. "2020-03".

end

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

interval

A logical parameter indicating whether calculations are to be made for the whole time interval (TRUE) or no (FALSE).

matched

A logical parameter indicating whether the matched sample approach is to be used (if yes, the parameter has the value TRUE).

contributions

A logical parameter indicating whether contributions of individual products are to be displayed. If it is TRUE, then contributions are calculated for the the base period start and the current period end.

prec

A numeric vector indicating precision, i.e. the number of decimal places for presenting results.

Value

This function returns the Montgomery price and quantity indicators and optionally also the price and quantity contributions of individual products.

References

Montgomery, J. K., (1929). Is There a Theoretically Correct Price Index of a Group of Commodities? Rome, International Institute of Agriculture

Examples

montgomery(milk, "2018-12", "2019-12", matched=TRUE, contributions=TRUE)
montgomery(coffee, start="2018-12", end="2019-03", interval=TRUE)