Power BI 中的按类别索引相当于分区上的 SQL row_number

问题描述

如何在 Power BI 的 M 中按类别添加索引并按列排序.我寻找等效的 SQL:

How to add index by category in M of Power BI with sorting by column. I look for equivalent of SQL:

ROW_NUMBER() over(partition by [Category] order by [Date] desc

假设我们有一张桌子:

+----------+-------+------------+
| Category | Value |    Date    |
+----------+-------+------------+
| apples   |     3 | 2018-07-01 |
| apples   |     2 | 2018-07-02 |
| apples   |     1 | 2018-07-03 |
| bananas  |     9 | 2018-07-01 |
| bananas  |     8 | 2018-07-02 |
| bananas  |     7 | 2018-07-03 |
+----------+-------+------------+

期望的结果是:

+----------+-------+------------+-------------------+
| Category | Value |    Date    | Index by category |
+----------+-------+------------+-------------------+
| apples   |     3 | 2018-07-01 |                 3 |
| apples   |     2 | 2018-07-02 |                 2 |
| apples   |     1 | 2018-07-03 |                 1 |
| bananas  |     9 | 2018-07-01 |                 3 |
| bananas  |     8 | 2018-07-02 |                 2 |
| bananas  |     7 | 2018-07-03 |                 1 |
+----------+-------+------------+-------------------+

表格的 PBI 代码:

PBI code for the table:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WSiwoyEktVtJRMgRiIwNDC10Dc10DQ6VYHSQ5I2Q5I1Q5Y2Q5Y7BcUmIeEIIkzZElTdAkLZAlTdEkLZElzZRiYwE=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type text) meta [Serialized.Text = true]) in type table [Category = _t, Value = _t, Date = _t])
in
    Source

推荐答案

感谢 Foxan Ng 和 Alexis Olson 提供有趣的 PBI 函数方法.我想为该集合添加其他方法.

Thank you, Foxan Ng and Alexis Olson, for interesting PBI function approach. I would like to add other approaches to the collection.

PBI 方法，没有功能:

The PBI approach, without function:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WSiwoyEktVtJRMgRiIwNDC10Dc10DQ6VYHSQ5I2Q5I1Q5Y2Q5Y7BcUmIeEIIkzZElTdAkLZAlTdEkLZElzZRiYwE=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type text) meta [Serialized.Text = true]) in type table [Category = _t, Value = _t, Date = _t]),
    #"Grouped rows" = Table.Group(Source, {"Category"}, {{"NiceTable", each Table.AddIndexColumn(Table.Sort(_,{{"Date", Order.Descending}} ), "Index",1,1), type table}} ),
    #"Expanded NiceTable" = Table.ExpandTableColumn(#"Grouped rows", "NiceTable", {"Value", "Date", "Index"}, {"Value", "Date", "Index"})
in
    #"Expanded NiceTable"

此解决方案的灵感来自 ImkeF 的解释:https://community.powerbi.com/t5/Desktop/Custom-column-Index-or-Ranking-by-other-column/td-p/33864/page/3

This solution has been inspired by ImkeF explanations here: https://community.powerbi.com/t5/Desktop/Custom-column-Index-or-Ranking-by-other-column/td-p/33864/page/3

这是我最喜欢的 R 方法.需要 dplyr 包.我喜欢它的简单性.

And here goes my favorite R approach. Requires dplyr package. I like it for its simplicity.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WSiwoyEktVtJRMgRiIwNDC10Dc10DQ6VYHSQ5I2Q5I1Q5Y2Q5Y7BcUmIeEIIkzZElTdAkLZAlTdEkLZElzZRiYwE=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type text) meta [Serialized.Text = true]) in type table [Category = _t, Value = _t, Date = _t]),
    #"Run R Script" = R.Execute("library(dplyr)#(lf)output <- dataset %>% group_by(Category) %>% mutate(row_no_by_category = row_number(desc(Date)))",[dataset=Source]),
    output = #"Run R Script"{[Name="output"]}[Value]
in
    output

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