monthBegin

Syntax

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

Alias: monthStart

Arguments

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

offset 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 is a positive integer. The default value is 1.

Details

Return the first day of the month that X belongs to.

If parameter offset is specified, the result is updated every n months. Parameter offset works only if parameter n>1.

Examples

$ monthBegin(2016.12.06);
2016.12.01

$ date=2016.04.12 2016.04.25 2016.05.12 2016.06.28 2016.07.10 2016.07.18 2016.08.02 2016.08.16 2016.09.26 2016.09.30
$ time = [09:34:07,09:36:42,09:36:51,09:36:59,09:32:47,09:35:26,09:34:16,09:34:26,09:38:12,09:38:13]
$ 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;

date	time	sym	qty	price
2016.05.12	09:30:00	MSFT	2200	49.6
2016.06.11	09:30:00	MSFT	1900	29.46
2016.07.11	09:30:00	MSFT	2100	29.52
2016.08.10	09:30:00	MSFT	3200	30.02
2016.09.09	09:30:00	MSFT	6800	174.97
2016.10.09	09:30:00	MSFT	5400	175.23
2016.11.08	09:30:00	MSFT	1300	50.76
2016.12.08	09:30:00	MSFT	2500	50.32
2017.01.07	09:30:00	MSFT	8800	51.29
2017.02.06	09:30:00	MSFT	4500	52.38

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

monthBegin_date	avg_price	sum_qty
2016.03.01	39.53	4100
2016.05.01	29.77	5300
2016.07.01	112.82	16000
2016.09.01	51.835	13300