value_index {PriceIndices}

Calculating the value index

Description

This function returns a value (or vector of values) of the value index

Usage

value_index(data, start, end, interval = FALSE)

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), quantities (as positive numeric) and prodID (as numeric, factor or character).

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 value indicating whether the function is to compare 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 calculated. In this latter case, all months from the time interval <start,end> are considered and start defines the base period (interval is set to TRUE).

Value

The function returns a value (or vector of values) of the value index. The value index is calculated as sum of expenditures from period end divided by sum of expenditures from period start.

References

(2004). Consumer Price Index Manual. Theory and practice. ILO/IMF/OECD/UNECE/Eurostat/The World Bank, International Labour Office (ILO), Geneva.

Examples

value_index(sugar, start="2019-01", end="2020-01")
value_index(sugar, start="2019-01", end="2020-01", interval=TRUE)