businessMonthBegin

businessMonthBegin(X, [offset], [n=1])

Return the first business day (Monday to Friday) of the month that X belongs to.

By default, each period corresponds to a calendar month, and the function returns the first business day of the month containing X. Here, business days are determined solely by the day of the week: Monday through Friday are considered business days, while Saturday and Sunday are considered non-business days. Public holidays and exchange trading calendars are not taken into account.

When both offset and n are specified and n > 1, the function calculates period start dates based on n-month periods. In this case, offset determines how the multi-month periods are aligned. Specifically, the system first calculates the first business day of the month containing offset and uses that date as the reference point. A new period boundary is then generated every n months, and the function returns the first business day corresponding to the period to which X belongs.

DolphinDB and pandas both provide similar date offset functionality at the conceptual level. For a comparison of calculation rules, see Functions Related to Date Offset.

X is a scalar/vector of data type DATE, DATEHOUR, DATETIME, TIMESTAMP or NANOTIMESTAMP.

offset (optional) is a scalar of the same data type as X. It must be no greater than the minimum value of X. The default value is the minimum value of X.

n (optional) is a positive integer. The default value is 1.

A scalar/vector of type DATE.

businessMonthBegin(2018.09.12);
// output: 2018.09.03

businessMonthBegin(2018.09.12, 2018.07.12, 3);
// output: 2018.07.02

date=2016.04.12+(1..10)*30
time = take(09:30:00, 10)
sym = take(`MSFT,10)
price= 49.6 29.46 29.52 30.02 174.97 175.23 50.76 50.32 51.29 52.38
qty = 2200 1900 2100 3200 6800 5400 1300 2500 8800 4500
t1 = table(date, time, sym, qty, price);
t1;

select avg(price),sum(qty) from t1 group by businessMonthBegin(date,2016.01.01,2);

Related functions: businessMonthEnd, monthBegin, monthEnd, semiMonthBegin, semiMonthEnd