Power BI

Multiple replacements or translations in Power BI and Power Query

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A common task when cleaning data is to perform multiple replacements at once. When dealing with “translation tables” you might have come across Chris Webb’s solution using List.Generate to deal with this. This works fine – but might deliver unexpected results if you don’t consider it’s implications properly. Say we add lines like shown below, then we might expect the result as highlighted in yellow:

Image2
Multiple replacements using 2 different techniques

So hey – what happened here?: Our catamaran turns out as a bearamaran and the chair turns to chwater.

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How to hack yourself in Power BI (and Power Pivot?)

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Reading Gerhard Brueckl’s post on how to visualize SSAS calculation dependencies reminded me of my post about a similar technique from December last year.

His solution has features that would do my version good as well:

  1. Directly connect to the model to be analysed without clumsy export of measures to txt via DAX Studio
  2. Including calculated columns? No!: Who does calculated columns in DAX in PBI? Do them in the query editor using M instead (more functions, better compression, easier merge of model to SSAS once needed)

So wouldn’t it be cool if we could just add a documentation page to our current model – “all in one” so to speak? Here you find how to “hack”-connect with Excel to your current Power BI Desktop-Model.

So what works with Excel should work with PBI as well – just that we need to connect via the query-editor, using M. And of course: As we’re hacking ourselves here (i.e. the file we’re currently working on), we need to save our changes in order to make them being shown.

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PowerBI Best Practice: Views for non-database data

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Marco Russo has shared bunch of very valuable PowerBI best practice tricks for designing your PowerBI model here: http://www.sqlbi.com/articles/data-import-best-practices-in-power-bi/?platform=hootsuite

One of them being never to directly import a database table, but to use a view instead as a kind of abstraction layer. It separates your business logic (that determines how the tables should be structured that will be passed into the data model) from your actual/incoming data (your source systems, whose table structure you cannot change and which might change itself over time).

This is really important in my eyes, as it will be only a question of time when your underlying data will change and the last thing you want to do is to edit all datamodels or even reports in your (multiple and possibly decentralized) PowerBI files!

But what do you do if your data don’t come from databases or you have no possibility to create views on them?

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How to share M-code in PowerBI and Power Query

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One of M’s advantages is that you can share M-code in textform and it will run instantly on a different computer. So no need to actually exchange a file. Provided that you pass the data on as well with your code, like you can see in this example.

But it would be a bit tedious to type in all the data manually – so let’s M do this automatically for us:

1 Automatically transfer a list into textform to share M-code

let
qList= {"This", "is", "a", "pretty", "short", "list"},
Source = qList,
CoreString = Text.Combine(List.Transform(Source, each Text.From(_)), """, """),
FullString = "= {"""& CoreString &"""}"
in
FullString

2 Automatically transfer a table into textform to share M-code

let
qTable= Table.PromoteHeaders(Table.FromColumns({ {"Column1" ,"This" ,"an" ,"shorter"}, {"Column2" ,"is" ,"even" ,"table"} })),
Source = qTable,
DemoteHeaders = Table.DemoteHeaders(Source),
ListOfColumns = Table.ToColumns(DemoteHeaders),
ConvertToTable = Table.FromList(ListOfColumns, Splitter.SplitByNothing(), null, null, ExtraValues.Error),
CoreString = Table.AddColumn(ConvertToTable, "Custom", each Text.Combine(List.Transform([Column1], each Text.From(_)),""" ,""")),
FullString = "= Table.PromoteHeaders(Table.FromColumns({ {"""& Text.Combine(CoreString[Custom], """}, {""")&"""} })),"
in
FullString

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How to handle M-code samples

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If you use Power Query or the query editor in Power BI every step you take will be recorded and translated to M-code. You can share this code and it will run in the new environment – so no need to actually exchange a file.

1 Check out what the M-code does

In order to make this code-sharing easy for beginners, I’m sharing my code in a way that it will run instantly with the test-data provided within the code. So you just copy my code examples into the advanced editor like this (example given for Power BI):

Home -> External Data -> Get Data -> Blank Query -> Home -> Query -> Advanced Editor.

There you replace all the content in the window: Check existing content, paste and click Done.

PasteCode

That’s all, now check out how it works: On the Home-tab check Close -> Close & Apply. This will load the data to the data model and you can build your reports with it.

2 Check out how the M-code does it

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