tmfirst
语法
tmfirst(T, X, window)
参数说明和窗口计算规则请参考：tmFunctions
详情
在给定长度（以时间 T 衡量）的滑动窗口内计算 X 的第一个元素。
例子
T = 1 1 1 2 5 6
X = 1 4 NULL -1 NULL 4
m = table(T as t,X as x)
select *, tmfirst(t, x, 3) from m| t | x | tmfirst_t |
|---|---|---|
| 1 | 1 | 1 |
| 1 | 4 | 1 |
| 1 | 1 | |
| 2 | -1 | 1 |
| 5 | ||
| 6 | 4 |
T = 2021.01.02 2021.01.02 2021.01.04 2021.01.05 2021.01.07 2021.01.08
X = 3 4 NULL -1 2 4
m = table(T as t,X as x)
select *, tmfirst(t, x, 3d) from m| t | x | tmfirst_t |
|---|---|---|
| 2021.01.02 | 3 | 3 |
| 2021.01.02 | 4 | 3 |
| 2021.01.04 | 3 | |
| 2021.01.05 | -1 | |
| 2021.01.07 | 2 | -1 |
| 2021.01.08 | 4 | 2 |
select *, tmfirst(t, x, 1w) from m| t | x | tmfirst_t |
|---|---|---|
| 2021.01.02 | 3 | 3 |
| 2021.01.02 | 4 | 3 |
| 2021.01.04 | 3 | |
| 2021.01.05 | -1 | 3 |
| 2021.01.07 | 2 | 3 |
| 2021.01.08 | 4 | 3 |