refmonth

Refmonth, short for reference month, is a term used in time series analysis and data reporting to designate a fixed calendar month that serves as a baseline or anchor for comparisons.

Definition: It refers to a specific year-month pair chosen to anchor calculations such as anomalies, growth rates, or seasonal adjustments. By comparing data from other months to the refmonth, analysts can measure relative changes or standardize monthly values across years.

Usage: In climatology, refmonth is used to compute anomalies relative to a baseline month; in economics, it can define a base period for index calculations; in survey or production data, it allows month-to-month comparability and coherent aggregation across periods.

Implementation: Refmonth is commonly stored as a string like "YYYY-MM" or as a date object. It is used to derive fields such as months since the refmonth or to compute month-over-month and year-over-year changes by anchoring calculations to the base value associated with the refmonth.

Example: If refmonth is 2020-01, monthly temperature anomalies might be calculated as the actual value minus the value in January 2020; in finance, an index may be normalized to a base value of 100 in January 2020, with subsequent months expressed relative to that base.

Considerations: The choice of refmonth should be explicit and well-documented, as it affects interpretation of results. Data gaps around the refmonth can bias adjustments, and different datasets or regions may select different refmonths. Consistency across calculations is essential for reliable comparisons.

See also: time series, baseline, anomaly, seasonality, index, normalization.