How to make this DAX code more efficient (less duplication).

[BlueSky]

The following table expression is working fine (it's to create exponential growth data for the Covid-19 virus, based on the virus doubling every x days.).

I'm still learning PowerBI and I'm struggling with variables (I know they work more as constants here) also not being able to do loops.

Could someone suggest how to make the code below more efficient, there is a lot of duplicaiton? 

(The only values which are changing are:

"Country" : 

Every 2 days, 

Every 3 days, 

Every 4 days, 

Every 5 days.

and 

The incremental factor, 

0.5,

0.333,

0.25,

0.2

However I'm having to repeat a lot of these values. (I've tried using varibles, in various places but get errors).

DimStartEnd =

union(

ADDCOLUMNS(

GENERATESERIES ( 0, 10, 0.5 ) // Doubles every 2 days

, "Days", [Value]/0.5+1

,"Deaths",round(10 * POWER(1+1, [Value] ),0 )

,"Country", "Every 2 days"

,"KeyFactToDimStartEnd","Every 2 days" &"-"& [Value]/0.5+1

)

,

ADDCOLUMNS(

GENERATESERIES ( 0, 10, 0.333 ) // Doubles every 3 days

, "Days", [Value]/0.333+1

,"Deaths",round(10 * POWER(1+1, [Value] ),0 )

,"Country", "Every 3 days"

,"KeyFactToDimStartEnd","Every 3 days" &"-"& [Value]/0.333+1

)

,

ADDCOLUMNS(

GENERATESERIES ( 0, 10, 0.25 ) // Doubles every 4 days

, "Days", [Value]/0.25+1

,"Deaths",round(10 * POWER(1+1, [Value] ),0 )

,"Country", "Every 4 days"

,"KeyFactToDimStartEnd","Every 4 days" &"-"& [Value]/0.25+1

)

,

ADDCOLUMNS(

GENERATESERIES ( 0, 10, 0.2 ) // Doubles every 5 days

, "Days", [Value]/0.2+1

,"Deaths",round(10 * POWER(1+1, [Value] ),0 )

,"Country", "Every 5 days"

,"KeyFactToDimStartEnd","Every 5 days" &"-"& [Value]/0.2+1

)

)

[Anonymous · Accepted solution]

EVALUATE
var __rates =
	SELECTCOLUMNS(
		{.5, 0.333, 0.25, 0.2},
		"GrowthRate",
			[Value]
	)
var __upperLimit = 10
var __output =
	GENERATE(
		__rates,
		var __currentRate = [GrowthRate]
		return
		ADDCOLUMNS(
			GENERATESERIES(1, __upperLimit, __currentRate ),
			"Days",
				round( [Value] / __currentRate + 1, 0),
			"Deaths",
				round(__upperLimit * POWER(2, [Value] ), 0 ),
			"Country",
				COMBINEVALUES(
					" ", // delimiter
					"Every",
					round(1 / __currentrate, 0),
					"days"
				),
			"KeyFactToDimStartEnd",
				COMBINEVALUES(
					" ",
					"Every",
					round(1 / __currentrate, 0),
					"days",
					"-",
					round( [Value] / __currentRate + 1, 0 )
				)
		)
	)	
return
	__output

Best

D

[BlueSky]

@Anonymous  thanks so much for writing this, it'll really help my learning! 🙂

[Mariusz]

Hi @BlueSky 

The below article will explain how to use variebles in DAX 

https://www.sqlbi.com/articles/variables-in-dax/

Best Regards,
Mariusz

If this post helps, then please consider Accepting it as the solution.

Please feel free to connect with me.
LinkedIn

[BlueSky]

I've already seen that article, the purpose of posting on here was for someone to help apply the theory in practice, which I've not been able to do without generating errors.