Variance Minus 1 month

[Anonymous]

Hello, I'm a beginner DAX/Power Bi and am stuck as to why my logic does not work or what the correct logic should be. I'm trying to find the variance (and then percentage of variance) from month to month of a dynamic 3 month average. Bascially did the average go up or down from the previous month by how much and what percent.

Here is what I have so far:

Variance = CALCULATE(SUM('ARTransactiontbl'[Positive Amount]),DATESINPERIOD('Date'[Date],LASTDATE('Date'[Date]),-3,MONTH))/3
-
DATEADD(CALCULATE(SUM('ARTransactiontbl'[Positive Amount]),DATESINPERIOD('Date'[Date],LASTDATE('Date'[Date]),-3,MONTH))/3,-1,MONTH)

[v-juanli-msft]

Hi @Anonymous

In your formula, DATEADD is used uncorrectly.  please read reference here to learn the usage.

Variance = CALCULATE(SUM('ARTransactiontbl'[Positive Amount]),DATESINPERIOD('Date'[Date],LASTDATE('Date'[Date]),-3,MONTH))/3
-
DATEADD(CALCULATE(SUM('ARTransactiontbl'[Positive Amount]),DATESINPERIOD('Date'[Date],LASTDATE('Date'[Date]),-3,MONTH))/3,-1,MONTH)

Based on my understanding, 

"a dynamic 3 month average" means, eg, 

for 2018/10, avg=(2018/8+2018/9+2018/10)/3

for 2018/11, avg=(2018/9+2018/10+2018/11)/3

for 2018/12, avg=(2018/10+2018/11+2018/12)/3

then the percentage of variance should be 

for 2018/10, (avg-2018/9)/2018/9

for 2018/11, (avg-2018/10)/2018/10

for 2018/12, (avg-2018/10)/2018/10

Is my understanding right?

Best Regards

Maggie

[Anonymous]

Hi Maggie,

I forgot to respond to your understanding - You are absolutely correct in your math.

Tom

[Anonymous]

Hi Maggie,

I though my use was correct. Your reference says: DATEADD(<dates>,<number_of_intervals>,<interval>)

My assupmtion: 

<dates>: (CALCULATE(SUM('ARTransactiontbl'[Positive Amount]),DATESINPERIOD('Date'[Date],LASTDATE('Date'[Date]),-3,MONTH))/3

<number_of_intervals>: -1

<interval>: MONTH

Is my assumption incorrect because I have the Calculated Sum as part of the <date>?

Sincerely,

Tom

[Greg_Deckler]

See if my Time Intelligence the Hard Way provides a different way of accomplishing what you are going for.

https://community.powerbi.com/t5/Quick-Measures-Gallery/Time-Intelligence-quot-The-Hard-Way-quot-TIT...