A generic SWITCH-function for the query editor in Power BI and Power Query

Although you can easily replicate the DAX SWITCH-function via list-, table- or record functions in M, I thought it would be convenient for many newbies to have a comfortable M-SWITCH-function that uses (almost) the same syntax than its DAX-equivalent:

    “Unknown month number”
DAX Formatter by SQLBI

The DAX-SWITCH-function will retrieve the content of its first argument (expression) ([Month]) and check it against he first parameters of the following pairs (value). If there is a match, the second parameter of the pairs (result, here: month name) is returned and if there is no match, “Unknown month number” will be returned.

How it works

The syntax for the M-function looks like so:

M.Switch(Expression as any, Values as list, Results as list, optional Else as text)

So we have 4 parameters: The Expression just like in DAX, but then the Values and Results come as separate lists. The last optional argument is just similar to DAX again.

This allows for a very convenient entry of function parameters:

1. You can quickly enter numerical ranges:

M.Switch(Month, {1..12}, {"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"}, "Unknown month number")

2. You can super-easily refer to switch-values in tables:

It has just one minor flaw: When you refer to a parameter or another query in the Expression-field, you will be default get an error first. But removing the 2 quotes will quickly fix it:

This is because I’ve set the format of this field to “any”, as the condition can actually be of any type. But the function-dialogue has no way to handle different types currently and will transform all entries to text by default in that case.

It uses a technique that I’ve used in this article already: There you can see that the results can also be functions for example.

Function code

Most of the code is documentation (row 7 onwards) or handles the missing values: Row 5+6 will return the value from the optional 4th argument (Else) if used, otherwise the default-value: “Value not found” will be returned. The main function logic (in row 4) is the positional index indicator: {List.PositionOf(Values, Expression)} that is applied to the list of Results. List.OfPositions will return the position (number) of where the Expression has been found in the list of Values. That x-th value will then be picked from the list.

Enjoy & stay queryious 😉

Web Scraping 1: Combine multiple tables from one page in Power BI and Power Query

This is a step-by-step description of how to combine multiple tables from one webpage into one table with categories as output. You can also apply this technique to combine tables from other sources as well (like from folder method for example or multiple different webpages (see in an upcoming article)).

Sometimes the page you want to scrape has multiple tables like here:

0 – Combine multiple tables into one: Input

And you want to combine them into 1 with a Category-column like so:

1 – Combine multiple tables into one: Result


I will present 2 methods here:

  1. Append-method: This is the obvious one and is fast for just a few tables.
  2. Add-Column-method: A bit more complicated but will be faster for a large number of tables and is also suitable for a dynamic number of tables.

You will also find 2 options at the end of this article:

  1. Use custom functions for multi-step table transformations
  2. Use dynamic filters to select the desired tables


Append method

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List.SelectPositions in Power BI and Power Query

With this new custom function “List.SelectPositions” you can easily select items from a list by just passing a list of their positions within it as the parameter.

What it does

Say you have a list with numbers {1..5} and want to select the 1st, 4th and 5th element from it. Then you can pass these positions to the function as another list: {0, 3, 4}.

ListSelectPositions({1..5}, {0, 3, 4}) will return: {1,4,5}

You see that I’ve decided to follow the zero-based counting principle here, that you find throughout M in the query editor. If you don’t like that, you can use the optional 3rd parameter to let it start to count from 1 instead:

ListSelectPositions({1..5}, {1, 4, 5}, 1) will return {1, 4, 5}

But if you have entered positions that don’t exist, the function will return an error in their positions by default:

ListSelectPositions({1..5}, {1, 4, 5}) will return {2, 5, Error}

because there is no 6th element (you’ve omitted the 3rd parameter that allows you to start counting with 1).

But you can change this behaviour as well through the last optional 4th parameter: Setting it to 0 will fill the missing positions with null like this:

ListSelectPositions({1..5}, {1, 4, 5}, null, 0) will return {2, 5, null}

and setting it to 1 will eliminate it and shorten the list like this:

ListSelectPositions({1..5}, {1, 4, 5}, null, 1) will return {2, 5}

These additional error-handling-options of the 4th parameters are useful for dealing with badly formatted data and if you want to learn more about it, just let me know in the comments so that I can prioritize it.

Function code

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Table.Group: Exploring the 5th element in Power BI and Power Query

In this post I’ll show you the magic stuff you can do with the 5th parameter (the optional comparer function) of the Table.Group M-function in Power BI and Power Query:

Table.Group parameters

  1. table as table,
  2. key as any,
  3. aggregatedColumns as list,
  4. optional groupKind as nullable number,
  5. optional comparer as nullable function

If you’re not familiar with the 4th parameter (groupKind) already, I strongly recommend to read Chris Webb’s article, as we will build on its knowledge here.

Another aspect worth mentioning for the modus in GroupKind.local is the performance aspect: It runs MUCH faster for large datasets than the default-setting. So if you are sure that your data will always be sorted accordingly, you can speed up your grouping-operations considerably. That means: Your data has to be sorted correctly by default. At least for my tests, you would loose the performance-gain once you’d sort your table by an explicit step before.

You can find an overview of comparer functions here.

Case insensitive grouping

Imagine there was a twist in Chris’ dataset and it would look like so:

Table.Group – Modified Source Data

We would probably not be happy with these results then:

Table.Group Problem with Case Sensitivity

Because M is by default case sensitive, we get more groups than we want. Let’s try Comparer.OrdinalIgnoreCase to the rescue then:

Pretty neat, isn’t it 😉  (You can use that comparer in other functions as well, see here for text- and list operations)

Something like this was what I’ve showed Huang Caiguang the other day, who asked me what the 5th parameter of this function was about (or so I understood). He then sent me a link to one of his articles, which demanded a good 2 hours for me to digest and understand: We can also use custom functions to create all different sorts of grouping behaviours here. These are my 2 favourites:

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Import text from pdf files in Power BI

While Power BI will soon provide functions to import tables from pdf-files, there might be occasions when you actually need to import text from pdf files (in unstructured form). With a little help from R in Power BI you can do exactly that. (And don’t worry: No need to learn R here: The necessary R-code is already included in my function below. All you need is to have R installed your machine). Please also note that at the time of writing the refresh of these queries in the service is only supported with the personal gateway and not with the enterprise version.


You can use the function below just like a normal M-function, just pass the (URL- or file-) path to it. All you have to take care of is that a instance of R is running on your machine. If this is new to you, check out Ruth Pozuelo’s video showing all the necessary steps: How to install R for Power BI

There is one package required: pdftools. The video above also shows how to install it.


Import text from PDF files:

You can try calling this function for a pdf-file from the internet like the M formula language specification like this:


If you want to import local files from your computer, just paste the full file-path instead of the URL. You don’t have to care about the direction of the slashes, both versions (forward and backwards) are accepted.

How to use

The script will return a table with one row for each page in the pdf-file by default. But it has an optional 2nd parameter that will return one row per pdf-text-line instead, if you put 1 into it. A page index and a row index will help navigating the result.

The 3rd parameter is an optional owner password for the pdf and the 4th the optional user password. If you’re using them, you have to enter null for the previous optional parameters. The following example shows how to use a user password while leaving the others “empty”:

ImportPdfText("MyPdfPath",null, null, "MyPassword")

Enjoy & stay queryious 🙂

Remove repeating characters from a string in Power BI and Power Query

Repeating spaces often cause problems when cleaning up your data. My new function “Text.RemoveRepeatingCharacters” can come to the rescue here.

Imagine you have a table like this:


To further work with this data, it would often be best if there was just one space between the words and not many.

The following function will do this for you:

Function Text.RemoveRepeatingCharacters

How to use

It takes 2 arguments: The Text/String and the Delimiter. The delimiter is an optional argument and by default set to space ” “. So you can leave it blank if that’s fine for you or enter a different value (like “,” for a comma) if needed.

How it works

It splits the text up into a list using the delimiter from the 2nd parameter (4: TextToList). Where one delimiter directly follows another, the element in the list will be empty. The next step (5: FilterList) then filters the list and removes these empty fields. In the last step (6: Result) the remaining (non-empty) fields will be reassembled, using the delimiter again. That way, just one delimiter will be left.

Edit 28-Jan-2018: While searching the web to see if one of my next blogpost-topics have already been published somewhere else already, I came across Ivan Bond’s blogpost who used this same technique over 2 years ago here: https://bondarenkoivan.wordpress.com/2015/10/11/transform-table-column-using-own-function-in-power-query/ . It’s a very good read and you will also learn how to use a function like this to transform an existing column instead of adding a new one to perform the operation like in my example above, so don’t miss it.

Enjoy & stay queryious 🙂

Date.DatesBetween to retrieve dates between 2 dates in Power BI and Power Query

Today I’m sharing a handy function with you that allows you to retrieve all or just a couple of dates between 2 given dates: Date.DatesBetween.


This function takes 3 parameters:

  1. From- or Start-date
  2. To- or End-date
  3. A selection of ONE of these intervals: Year, Quarter, Month, Week or Day

All dates will be created at the end of the chosen interval: So if you want to analyse events with a duration for example, where you want to transform your data to show one day per (monthly) event, this function generates month-end-dates for every month within the timespan. Please not that if the To-/End-date is within a month, the last element of the list will NOT be that day, but the day of the end of that month.

The default-value for the 3rd parameter is “Day”, so if you omit the specification, the function will return a list of all days in between.

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Right Aligning Text in Power BI: Format Improvements for Easy Profit&Loss Reports

Edit 14-Dec-2017: Now that we can right-align text measures in PowerBI, a SWITCH-measure like here: http://www.thebiccountant.com/2017/04/24/kpis-in-easy-profit-and-loss-for-powerbi/#comment-719 is the best alternative in my eyes. No need to read on 🙂

As shown in my last part of the Easy P&L-series, Power BI unfortunately still lacks some fundamental formatting options like:

  1. Right aligning text (please vote for it here: Right align text in Power BI – edit 15th Nov: We’re there: Right aligning text is available now: https://powerbi.microsoft.com/en-us/blog/power-bi-desktop-november-2017-feature-summary/)
  2. Display numbers in different formats within one column (either to be implemented as a “neutral” format for Switch-measures, where the referenced measures carry the formatting attributes already, or as a part of a formula-based conditional formatting) (Thanks Matt for the voting-link: Conditional format SWITCH measure)

So for the moment I choose between the following workaround-options:

  1. Display %-values in a separate column
  2. Format numbers as text and fill up with spaces so that all end up right aligned
  3. See the suggestion from Matt Allington in the comments below (very nice)

Right aligning text or percentage figure in new column

For both options the preparations are the same:

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Bulk-extracting Power Query M-code from multiple pbix files in Power BI

If you want to audit or analyse the M-code of multiple Power BI pbix-files at once, you start with either:

  1. a from-folder query where you filter all files of interest or
  2. a table with the full file-path-specification of the files to be analysed in “Column1”.

Then you add a column where you call the function that extracts the M-code:

Function to extract the M-code

This code is a variation of Igors function which retrieves the code from an opened pbix-file. So now you can apply it to closed pbix-files as well.

For method 1 you call it like so (as it takes the full string for the file-path as its parameter):

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Create a function library in Power BI using M-Extensions

Having the ability to use own M-function the same way than native functions in Power BI and Excel has been one of my biggest wishes for quite some time. So I was more than amazed to see Frank Tonsen’s comment showing a way to do exactly this in PowerBI, that has been available for almost half a year now: M-Extensions as part of the custom connectors.

Unlike custom connectors who show up in the import-dialogue and provide a custom tailored option for importing data or creating queries, M-Extensions don’t show up explicitly anywhere in Power BI: They just do their M(agic) job to make the functions that you’ve defined in them accessible, as if they were inbuilt native functions: Type their name into the formula bar like this (1):

And enjoy the function description (2: if you’ve specified it in the definition, which is optional):

Simplest example

  1. Your functions: Number.Double and Number.Triple
  2. Combined with the keyword “shared” and separated by “;”
  3. Prefix by “section MyLibrary” gives this text:
section MyLibrary;
shared Number.Double = (Number as number) =>
2 * Number;
shared Number.Triple = (Number as number) =>
3 * Number;


How to make M-Extensions work

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