TiBCO Spotfire-如何仅计算数据的最后3列-请参见descr

Question

Week    Sales
1   100
2   250
3   350
4   145
5   987
6   26
7   32
8   156

I wanted to calculate the sales only for the last 3 weeks so the total will be 156+32+26. 我只想计算最近3周的销售额，所以总数将为156 + 32 + 26。

If new weeks are added it should automatically calculate only the data from the last 3 rows. 如果添加了新的星期，则应该仅自动计算最近3行中的数据。

Tried this formula but it is returning an incorrect sum 尝试过此公式，但返回不正确的总和

sum(sales) over (lastperiod(3(week))

Answer 1

If you want only the last 3 weeks sum in calculated column you can use a simple if calculation. 如果只想在计算列中提供最近3周的总和，则可以使用简单的if计算。

If([week]>(Max([week]) - 3),Sum([sales]),0)

If you need 3 weeks calculation throughout table use below one. 如果您需要在整个表格中进行3周的计算，请使用以下一项。

sum([sales]) OVER (LastPeriods(3,[week]))