Unfill in Power Query

Recently I received a question on how to Unfill in Power Query.  In other words, we want the opposite of the Fill feature, which fills data into blank cells (cells that contain a null value.)  If we see repeating values, we’d like to keep only the first, then replace all subsequent duplicate values with the null keyword.

Now I’ll be honest that I’d typically never do this.  I’d load the values into a table, then use a PivotTable to show the data the way I want to see it:

A table with repeating values, and a pivottable that suppresses repeating values

But having said this, if you need to have your data look like this…

A table of Animals, Colour and Amount that shows blanks under each repeating animal

… well then why not?

Unfill data with Power Query – Step 1

The first thing we need to do is run our recipe for numbering grouped rows.  (You can find this in our Power Query Recipe Cards, or in our Power Query Academy videos.)

Namely, it looks like this:

  • Sort the data by Animal to order it
  • Group the data by Animal
    • Add a single aggregation called “Data” for All Rows
  • Go to Add Column -> Custom Column and use the following formula
    • =Table.AddIndexColumn([Data],"Row",1,1)
  • Right click the “Custom” column -> Remove Other Columns
  • Expand all columns from the Custom Column

You’ve now got your rows numbered:

A Power Query showing Animal, Amount, Colour and a Row Number where each row with the same animal has a unique value starting from one

Unfill data with Power Query – Step 2

Once you’re in this state, it actually becomes pretty easy:

  • Go to Add Column -> Custom Column and use the following formula
    • = if [Row] = 1 then [Animal] else null
  • Remove the [Animal] column and the [Row] columns
  • Re-order the columns as desired
  • Rename [Custom] to Animal
  • Set the data types

Once done, you’ll notice that we have unfilled the data nicely.

A Power Query showing Animal, Colour and Amount, but only the first instance of a Animal is shown in the Animal column with duplicates showing as null

Final Thoughts

As I mentioned at the outset, this isn’t something I ever anticipate myself doing.  But if you do have a good business use case, I’d be curious to know what it is.  (I assume the asker did – although it came from a comment on an old blog post, so haven’t been able to ask.)  Please share in the comments. ?

Remove Dynamic Number of Top Rows

Removing the top five rows from a data set is easy in Power Query, but what do you do when the number of rows changes?  There isn’t a built-in Remove Dynamic Number of Top Rows function.  In this post we’ll look at how to set this up.

Illustration of the issue

Assume you have the following report, and you’re only interested in the Cider sales:

With Cider starting in row 9, we’d need to remove the top 8 rows.  That’s fairly easy.  You just need to:

  • Go to Remove Rows -> Remove Top Rows -> 8
  • Promote headers
  • Do whatever else you need to do to the data

But then you get an updated version of the data set, and it looks like this:

Uh oh.  Best case, if you run the previously generated Power Query script, you’ll end up with the following result:

But more likely, if you promoted the clean header row from the original data set, you’ll get a step level error since the revised data set doesn’t yield a “Cider” column when row 1 (shown above) is promoted to header:

Regardless of which one of these scenarios appears worse to you, I think we can agree that neither one is desired.  So how do we make this work on a dynamic basis?

Solution Architecture

The way I approach this issue is to split the job into 3 queries as follows:

Let’s look at how this works in practice…

Query 1:    Raw Data

The purpose of this query is quite simple:

  • Connect to the Raw Data source
  • Perform any preliminary cleanup
  • Rename the query as “Raw Data” (add something descriptive if you have many data sources
  • Set the query to load as a Connection Only query (disable the load in Power BI)

The key thing to note here is that we’re not doing any work to remove top rows beyond things that we know will ALWAYS occur.  We may want to drop columns and other things to reduce our data set, we just don’t want to touch anything we can’t guarantee will be exactly the same when we get updated data.

In the case of the data sample I showed above, I’m just going to connect to the data set and load it as connection only.  (While I could make an argument that the first 3 rows will always need to go, I will get rid of those when filtering to just the cider header anyway.)

Query 2:    Generate the Dynamic Row Number

The next step is to generate the number that will indicates the dynamic number of top rows we are looking for.  Despite the fact that the row which holds our data is changing, this is actually relatively easy once you know how:

  • Right click the Raw Data query -> Reference
  • Go to Add Column -> Add Index Column -> From 0
  • Filter one of the columns to the data you are looking for
  • Right click the [Index] Column -> Remove Other Columns
  • Go to Home -> Keep Rows -> Keep Top Rows -> 1
  • Right click the value in the cell -> Drill Down
  • Rename the query as “HeaderRows”
  • Set the query to load as a Connection Only query (disable the load in Power BI)

You now have a query that will dynamically pick up the number of rows to be removed from the top of the data set before it encounters the text you are looking for.

Step 3:       Remove Dynamic Number of Top Rows

So now comes the magical part:

  • Right click the Raw Data query -> Reference
  • Go to Home -> Remove Rows -> Remove Top Rows
  • Type in the current number of rows to remove (for this example, we’ll assume it is 8 rows)

The formula bar will now be showing the formula =Table.Skip(Source, x ) where x is the value you typed in:

  • Replace the value with “HeaderRows”

CAUTION!  Power Query is case sensitive.  You must spell and case HeaderRows EXACTLY as you did previously.  And if you separated those two words with a space, you need to escape it with hash marks and quotes:  #"Header Rows"

If you’ve replaced everything correctly, you should see that everything still works:

Does it Work?

Here’s what we see when we point RawData to the second data set I showed earlier:

The sample file for this example can be downloaded here.

Power Query Challenge 7 – Phone Words

Yesterday, Nick (one of our forum users) posted a Phone Words challenge in our forum, which looks like a great candidate for Power Query Challenge #7.  I haven't had time to tackle it myself, but if you're up for a Friday challenge, why not give it a go?

1-800-Get-Data converts to 1-800-438-3282

Here's the Challenge (word for word):

Take any Phone # and convert it to all possible Letters aka Phone Words.
Phone # can be input any format (strip out all other characters)

Example:

536-7857 = Ken Puls, etc...

Here's the thread where you can post your solution.

Thanks Nick!

PS, if anyone else has challenges they'd like to post, I'm more than happy to set them up in this series.  Obviously it's been a bit quiet here lately, for reasons that we hope to announce soon!

Values Become Text After UnPivoting Other Columns

Have you ever set up a nice query to UnPivot other columns, only to find that the query data types change when you add new columns?  This post will cover why values become text after unpivoting other columns.

Background

We’ve got a nice little table called “Data” showing here.  Nothing special, it just summarizes sales by region by month, and our goal is to unpivot this so that we can use it in future Pivot Tables.  (You can download the source file here.)

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Now, you will notice that April’s sales are outside the table. This is by design, and we’ll pull it in to the table later when we want to break things.  Smile

UnPivoting Other Columns – The Hopeful Start

If you’ve been following my blog for any period of time, you’ve seen this, but let’s quickly go over how to unpivot this:

  • Select a cell in the table
  • Go to Power Query (or Data in Excel 2016) –> From Table

We’re now looking at the Power Query preview of the table:

image

Great, now to unpivot…

  • Hold down the Shift key and select the Country and Prov/State column
  • Right click the header of either of the selected columns and choose Unpivot Other Columns
  • Right click the headers of the two new columns and rename them as follows:
    • Attribute –> Month
    • Value –> Sales

Re-Pivoting from the Data Model

With the table complete, I’m going to load this to the data model and create a Pivot Table:

  • Go to Home –> Close & Load –> Close & Load To…
  • Choose to Load to the Data Model

The steps to create the Pivot depend on your version of Excel:

  • Excel 2013: Go in to Power Pivot –> Home –> PivotTable and choose a location to create it
  • Excel 2016: Click any blank cell and go to Insert –> PivotTable.  As you have no data source selected, it will default to using the data model as your source:

Iimage

With the PivotTable created, I’ve configured it as follows:

  • Rows:  Country, Prov/State
  • Columns:  Month
  • Values:  Sales

And that gives me a nice Pivot like this:

image

Let’s Break This…

Okay, so all is good so far, what’s the issue?  Now we’re going to break things.  To do that, we’re going to go back to our original data table and expand the range:

image

In the picture above, I’ve left clicked and dragged the tiny little widget in the bottom right corner of the table to the right.  The table frame is expanding, and when I let go the Apr column turns blue, indicating that it is now in the boundaries of the table.

With that done, I’m going to right click and refresh my Pivot Table, leaving me with this:

image

Huh?  Why was the sales measure removed?  And if I drag it back to the table, I get a COUNT, not a SUM of the values?  And even worse, when I try and flip it back to SUM, I’m told that you can’t?  What the heck is going on here?

image

Importance of Power Query Step Order

To cut to the chase, the issue here is that when we first created the table in the data model, the Sales column was passed as values.  But when we updated the data to include the new column, then Sales column was then passed entirely as text, not values.  Naturally, Power Pivot freaks out when you ask for the SUM of textual columns.

The big question though, is why.  So let’s look back at our query.

Our original data set

If we edit our query, we see that the steps look like this:

image

To review this quickly, here’s what happened originally

  • Source is the connection that streams in the source data with the following columns:

image

  • Changed Type set the data type for all the columns.  In this case the Country and Prov/State fields were set to text, and the Jan, Feb & Mar columns were set to whole number.  We can see this by looking at the icons in the header:

image

Note that if you don’t have these icons, you should download a newer version of Power Query, as this feature is available to you and is SUPER handy

 

  • We then selected the Country and Prov/State columns and chose to Unpivot Other Columns.  Doing so returned a table with the following headers

image

Notice that the first three columns are all textual, but Sales is showing a numeric format?  Interestingly, it’s showing a decimal format now, but it shows the numeric format because all unpivoted columns had explicitly defined numeric formats already.

The final steps we did was to rename our columns and load to the data model, but the data types have been defined, so they were sent to the data model with Sales being a numeric type.

Why Values Become Text After UnPivoting Other Columns

Okay, so now that we know what happened, let’s look at what we get when we step through the updated data set.

  • First we pulled in all the columns.  We can plainly see that we have the new Apr column:

image

  • The Changed Type step is then applied:

image

Hmm… do you see that last data type?  Something is off here…

So when we originally created this query, Power Query helpfully pulled in the data and applied data types to all the existing columns.  The problem here is two-fold:  First, the Apr column didn’t exist at the time.  The second problem is that Power Query’s M language uses hard coded names when it sets the data types.  The end effect is that upon refresh, only the original columns have data types defined, leaving the new columns with a data type of “any” (or undefined if you prefer).

  • We then unpivoted the data, but now we see a difference in the output

image

Check out that Value column.  Previously this was a decimal number, now it’s an “any” data type.  Why?  Because there were multiple data types across the columns to be unpvioted, so Power Query doesn’t know which was the correct one.  If one was legitimately text and Power Query forced a numeric format on it you’d get errors, so they err on the side of caution here.  The problem is that this has a serious effect on the end load to Power Pivot…

  • Finally, we renamed the last two columns… which works nicely, but it doesn’t change the data type:

image

Okay, so who cares, right?  There is still a number in the “any” format, so what gives?

What you get here depends on where you load your data.  If you load it to the Excel worksheet, these will all be interpreted as values.  But Power Pivot is a totally different case.  Power Pivot defaults any column defined as “any” to a Text data type, resulting in the problems we’ve already seen.

Fixing the Issue

For as long as we’ve been teaching our Power Query Workshop, we’ve advocated defining data types as the last step you should do in your query, and this is exactly the reason why.  In fact, you don’t even need to define your data types in the mid point of this one, that’s just Power Query trying to be helpful.  To fix this query, here’s what I would recommend doing:

  • Delete the existing Changed Type step
  • Select the final step in the query (Renamed Columns)
  • Set the data type for each column to Text except the Sales column, which should be Decimal Number (or currency if you prefer)

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When this is re-loaded to the Data Model, you’ll again be able to get the values showing on the Pivot Table as Sum of Sales.

Avoiding the Issue

Now, if you don’t want Power Query automatically choosing data types for you, there is a setting to toggle this.  The only problem is that it is controlled at a Workbook level, not at a global Excel level.  So if you don’t mind setting it for every new workbook, you can do so under the Power Query settings:

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Is Changed Type Designed in the Correct Way?

It’s a tough call to figure out the best way to handle this.  Should the data types be automatically hard coded each time you add a new column?  If the UnPivot command had injected a Changed Type step automatically, we wouldn’t have seen this issue happen.  On the other hand, if a textual value did creep in there, we’d get an error, which would show up as a blank value when loaded to Power Pivot.  Maybe that’s fine in this case, but I can certainly see where that might not be desirable.

Personally, I’d prefer to get a prompt when leaving a query if my final step wasn’t defining data types.  Something along the lines of “We noticed your final step doesn’t declare data types.  Would you like me to do this for you now (recommended)” or something similar.  I do see this as an alternate to the up-front data type declaration, but to be honest, I think it would be a more logical place.