weekBegin

weekBegin(X, [weekday=0], [offset], [n=1])

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

weekday (optional) is an integer from 0 to 6. 0 means Monday, 1 means Tuesday, ..., and 6 means Sunday. The default value is 0.

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.

For each element of X, return the first date of the week that it belongs to and that starts on the day as specified by parameter weekday.

• If parameter weekday>weekday(X, false): for each element of X, return a date that corresponds to the specified weekday parameter in the previous calendar week.

• If parameter weekday<=weekday(X, false): for each element of X, return a date that corresponds to the specified weekday parameter in the same calendar week.

If parameter offset is specified, the result is updated every n weeks. Please refer to example 2 below. Parameter offset works only if parameter n>1.

Example 1

t = table(2017.12.01..2017.12.14 as date);
update t set weekday=weekday(date, false), weekBegin=weekBegin(date), weekBegin4=weekBegin(date,4);
t;

Example 2

 t = table(2018.01.03+0..10*3 as date, 0..10 as x);
 update t set weekday=weekday(date, false), weekBegin=weekBegin(date,,2018.01.02,2);
 t;

Example 3

date=2012.10.02 2012.10.03 2012.10.07 2012.10.08 2012.10.12 2012.10.16 2012.10.18 2012.10.20 2012.10.25 2012.10.28
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;

select avg(price),sum(qty) from t1 group by weekBegin(date, 4, 2012.10.01, 2);

Related function: weekEnd