The function returns Pearson's correlation coefficients between price and quantity of products with given IDs and sold in the time interval: <start, end>. Correlation coefficients are calculated for each month separately. Results are presented in tabular or graphical form depending on the figure parameter.
Arguments
data
The user's data frame. 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) with unique product IDs.
start
The beginning of the considered time interval (as character) limited to the year and month, e.g. "2020-03".
end
The end of the considered time interval (as character) limited to the year and month, e.g. "2020-04".
figure
A logical parameter indicating whether the function returns a figure (TRUE) or a data frame (FALSE) with price-quantity correlations.
date_breaks
A string giving the distance between breaks on the X axis like "1 month" (default value) or "4 months".
set
The set of unique product IDs to be used for determining correlation between prices and quantities of sold products (see also data_matching). If the set is empty, the function works for all products being available in period.