Posts Tagged ‘Function’

Dynamically create types from text with Type.FromText in Power Query and Power BI

In this article I’ll show you how to create types from text in Power Query, enabling you to dynamically change types via functions for example. It’ll come out as a custom Type.FromText function which has been asked for in the comments of this article: https://www.thebiccountant.com/2017/01/09/dynamic-bulk-type-transformation-in-power-query-power-bi-and-m.

Problem

To transform a column to type text can be done like so:

Table.TransformColumnTypes(Source,{{"Column1", type text}})

This transforms the “Column1” from table “Source” to type text.  Now, if you want to make the type dynamic and move it to a function parameter like so:

(VariableType as type) =>

Table.TransformColumnTypes(Source,{{"Column1", VariableType}})

This returns a function dialogue as follows:

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The full Table.ContainsAnywhere function for Power Query in Power BI and Excel

In a previous post I introduced the concept of a function that searches for an occurrence of a character or string within all columns of a table. Here I share the full “Table.ContainsAnywhere” – function with parameters for many useful options.

Function parameters and options

  1.  The first parameter “MyTable” refers to the table to search through
  2.  The 2nd parameter “MySearchStrings” can be either a text field or a list of strings to be searched for. The function will take care of any of these cases automatically.
  3.  If the 2nd parameter is a list and this 3rd parameter is null or not speified, the function will return true if any of the list items is found within the table. But if set to “All”, all list items have to be found somewhere in the table for the function to return true.
  4.  By default, the search will be made in a case sensitive mode (as this is the default-mode in Power Query). But any entry into the 4th function parameter will turn this to a case insensitive mode instead.
  5.  By default, the string or list entry has to match fully with any entry in the table. Again, any entry in the 5th parameter swaps that to a partial match.

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A new Table.ContainsAnywhere function for Power Query in Power BI and Excel

The native Table.Contains-function in Power Query tells you if one or more strings are included in one or more of its columns. But you have to be specific about which strings you search in which column. But what to do if you want to search a string in all of its columns instead? Use my new Table.ContainsAnywhere function.

Problem

In the native function, you have to pass in a record with search term and column name. So if you search for “blue” in column “Description”, your formula would look like so:

Table.Contains( YourTableName, [Description = "blue"] )

But that’s not what I want in this case. I want the formula to search through all columns within the table for the occurrence of “blue”.

Solution

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Improved Text.SplitAny – function for Power BI and Power Query

Today I’ll present an adjustment to the Text.SplitAny – function in Power BI’s query editor or Power Query. The native function takes a string as an input and splits the text by every character that is contained in the string. This seems fairly unusual to me and I haven’t used that function very often.

Problem

But what I have come across fairly often is the requirement to split a string by a bunch of different (whole) strings (instead of single characters).

Solution

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Fast and easy way to reference previous or next rows in Power Query or Power BI

When you search the web for solutions to reference previous or next rows in the query editor of Power BI or Power Query, you will find many solutions that base on an added index-column. But the problem with these solutions on large tables is that performance will range between slow and extremely slow. In this post I’ll show a faster method with function Table.ReferenceDifferentRow .

Basic mechanism

This new mechanism doesn’t use an index that is either used to merge the table with itself or to be referenced as a new row index. Instead, I “simply” add one table next to the other. To retrieve the previous row from a table, I reference the original table, delete its last row and add a blank row on top. That will “shift” the first row to the second row. Then I “put” this table just right to the original table, without referencing a key or applying any sort of logic. This will speed up the process considerably:

Shift table to reference different rows

The key of this method is the Table.FromColumns-function: It creates a table from a list of columns in the order of the columns in the list. So I just have to find a way to turn 2 tables into 1 list of columns:

Table.ToColumns(OriginalTable) & Table.ToColumns(ShiftedTable)

will do this job. Table.ToColumns will turn a table into a list of columns and the ampersand (“&”) will concatenate the lists from both tables.

The functions

The basic function that references the previous row of a column looks like so:

Reference your table in the 1st parameter and the give the column name whose previous row you want to see as the 2nd parameter.

But I’ve also included this basic mechanism into a handy function with some bells and whistles: “Table.ReferenceDifferentRow” Please be aware, that this function is not as fast as the main simple function!

 

How the Table.DifferentRow-function works

  1. The only mandatory parameter is your table and then it will return a table with the previous rows values of all columns. So fnTable_ReferenceDifferentRow(MyTable) will return the result from above.
  2. The default-value for this parameter is set to -1 to return the previous row if you omit it. If you want the values from the next row instead, fill in 1. 2 will return the overnext and -2 the pre-previous row. This is what fnTable_ReferenceDifferentRow(MyTable, -2) returns:

    -2 will return the pre-previous row

     

  3. You probably just need one or a few columns/fields from the previous row: In the 3rd parameter you can enter a list of column names to be returned:   fnTable_ReferenceDifferentRow(MyTable, null, {"Value"}):

    Select specific columns

     

  4. Quite often the previous values shall only be returned within a group of rows. (That’s when you use [MyColumn] = EARLIER([MyColumn]) in DAX). You can enter a list of group-columns in the 4th parameter of this function: fnTable_ReferenceDifferentRow(MyTable, null, null, {"Product"})

    Group by columns

  5. By default, the suffix “.Prev” will be added to the new column names. Use the 5th parameter to change if needed. In this example, I reference the row below using “1” for the 2nd parameter: fnTable_ReferenceDifferentRow(MyTable, 1, null, null, "Next")

    Changing suffix and referencing next row

  6. If performance is still too bad, you can try to buffer the input table. Any value in the 6th parameter will do that for you (although I haven’t seen a performance improvement for my test cases).

How to apply the function

Please check out this short video on how to apply the function

 

Why not use DAX?

Referencing a previous row in DAX is still faster than my method above. So if you can do it in DAX, go ahead (create an index in the query editor and use LOOKUPVALUE like shown here: https://powerpivotpro.com/2015/03/how-to-compare-the-current-row-to-the-previous-row-in-power-pivot/. ) My function is for cases where you have to stay in M.

Enjoy & stay queryious 😉

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:

SWITCH (
[Month],
    1, “January”,
    2, “February”,
    3, “March”,
    4, “April”,
    5, “May”,
    6, “June”,
    7, “July”,
    8, “August”,
    9, “September”,
    10, “October”,
    11, “November”,
    12, “December”,
    “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:

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