Replacing values in multiple columns based on condition in Power Query

[Anonymous]

Hello,

I have a table like this:

Date	plan	unplan	internal	external	production	day flag
1/1/2020	0	0	50	70	6000	Production Day
1/2/2020	0	0	0	0	0	Non-Production Day
1/3/2020	0	0	100	200	1300	Down Day
1/4/2020	0	0	30	80	5000	Production Day
1/5/2020	0	0	120	150	1000	Down Day
1/6/2020	0	0	0	0	0	Non-Production Day
1/7/2020	0	0	0	0	0	Non-Production Day

if [day flag] = "Down Day" then replace [plan], [unplan], [internal] and [external] columns with null, else keep original values.

The result like this:

Date	plan	unplan	internal	external	production	day flag
1/1/2020	0	0	50	70	6000	Production Day
1/2/2020	0	0	0	0	0	Non-Production Day
1/3/2020	null	null	null	null	1300	Down Day
1/4/2020	0	0	30	80	5000	Production Day
1/5/2020	null	null	null	null	1000	Down Day
1/6/2020	0	0	0	0	0	Non-Production Day
1/7/2020	0	0	0	0	0	Non-Production Day

I use code:

#"Replaced Value1" = Table.ReplaceValue(Source, each [plan], each if [day flag] = "Down Day" then null else [plan],Replacer.ReplaceValue,{"plan"}),
#"Replaced Value2" = Table.ReplaceValue(#"Replaced Value1",each [unplan], each if [day flag] = "Down Day" then null else [unplan], Replacer.ReplaceValue,{"unplan"}),
#"Replaced Value3" = ...

#"Replaced Value4" = ...

As you see, I have to repeat same logic 4 times for replace values of [plan], [unplan], [internal] and [external] columns. Actually, in my table, there are 20 columns need do that. I don't want to repeat this logic 20 times.

I was wondering if any better solution for my situation?

Thanks!

[ziying35 · Accepted solution]

Hi, @Anonymous 

Based on the simulated data source and the data processing logic you provided, write the query code like this:

= Table.ReplaceValue(Source, each [day flag]="Down Day", null, (x,y,z)=> if y then z else x, List.Range(Table.ColumnNames(Source),1,4))

If my code solves your problem, mark it as a solution

[Rickmaurinus]

Another way to do it, is the unpivot your columns, and then on the newly created column apply a conditional replace operation. 

= Table.ReplaceValue(
     #"Changed Type",
     each [Value],
     each if [day flag] = "Down Day" then null else [Value],
     Replacer.ReplaceValue,{"Value"}
 )

You can find the details on the conditional replace right here: 

https://gorilla.bi/power-query/replace-values/#conditionally-replace-values

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[v-alq-msft · Accepted solution]

Hi, @Anonymous 

As what is suggested by @ziying35 , I created data to reproduce your scenario. The pbix file is attached in the end.

Table:

You may insert a new step as below. On your side, you may add all corresponding columns in {"plan","unplan","internal","external",...}.

= Table.ReplaceValue(Source, each [day flag]="Down Day", null, (x,y,z)=> if y then z else x, List.Select(Table.ColumnNames(#"Changed Type"),
each  List.Contains( {"plan","unplan","internal","external"},_)
)
)

Result:

Best Regards

Allan

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[Anonymous]

Thank you very much! Your demostration is really very helpful for understanding the code. It works on my end!

[ziying35 · Accepted solution]

Hi, @Anonymous 

Based on the simulated data source and the data processing logic you provided, write the query code like this:

= Table.ReplaceValue(Source, each [day flag]="Down Day", null, (x,y,z)=> if y then z else x, List.Range(Table.ColumnNames(Source),1,4))

If my code solves your problem, mark it as a solution

[Rickmaurinus]

Hey ziying35.

I included your solution in my blogpost at https://gorilla.bi/power-query/replace-values/. 

However, I'm accustomed to working with Replacer.ReplaceValues and Replacer.ReplaceText. I don't fully understand your example. 

Can you elaborate on the inner workings of : 

(x,y,z)=> if y then z else x?

Warm regards,

Rick

[ziying35]

Simple understanding: the second parameter of the function Table.ReplaceValue is represented by y, the third parameter is represented by z, and the replaced element itself is represented by x

[Rickmaurinus]

Hi ziying,

Thanks for adding the clarification. I could imagine in my head that happens. I'm just stumbled by how you thought of doing this, please help me understand. 

No where does it say that Y represents the Table function, or that the third parameters should be the Z or what X should do. 

If I can ask

1. How did you come up with this in the first place? Is there any documentation on this? 

2. In theory, you could have replaced the function letters with any other letter, correct? 

Best,

Rick

[ziying35]

1. this use, I also happened to see in other places, I can not remember the place,.
2. Yes, there is nothing wrong, you can use any other letters instead

[lbendlin]

You can replace it with any string you want.

(original,logiccheck,alternative)=> if logiccheck then alternative else original

Yes, the documentation is a bit sparse on this.  Here's a slight hint:

Replacer.ReplaceValue - PowerQuery M | Microsoft Docs

It's misleading, but at least it mentions parameters 🙂

I have a suspicion that this approach can be used for other M functions as well.  Didn't have time to test it yet.

[lbendlin]

x = original value

y = match condition  (true or false)

z = replacement value

[edhans]

You can include multiple columns in the list. This is a text replacement. Just add more columns in the list brackets {}

Table.ReplaceValue(#"Filtered Rows","a","g",Replacer.ReplaceText,{"Stock Item", "Color", "Selling Package"})