Adding date column that grows with numbe of rows

[Anonymous]

In Power BI, I forecasted Value column using R in the Power Query editor. Then, once I had the forecasted value, I appended it to the original table, which resulted in something like this:

Date	Value
1/01/2021	5245
2/01/2021	3214
3/01/2021	7458
4/01/2021	36314
5/01/2021	5478
	2314
	5478
	63211
	2314
	52336
	1247

Now I want to add date to the projected values, creating rolling date rows that keeps groowing as the number of rows grows.

The final value should seem as follows:

Date	Value
1/01/2021	5245
2/01/2021	3214
3/01/2021	7458
4/01/2021	36314
5/01/2021	5478
6/1/2021	2314
7/1/2021	5478
8/1/2021	63211
9/1/2021	2314
10/1/2021	52336
11/1/2021	1247

OR

Add a new date column as follows: 

Date	Value	New   Date
1/01/2021	5245	1/01/2021
2/01/2021	3214	2/01/2021
3/01/2021	7458	3/01/2021
4/01/2021	36314	4/01/2021
5/01/2021	5478	5/01/2021
	2314	6/1/2021
	5478	7/1/2021
	63211	8/1/2021
	2314	9/1/2021
	52336	10/1/2021
	1247	11/1/2021

I did a lot of googling and spent a lot of time on this (almost half a day), but I couldn't find anything useful. And now the Power BI community is my only hope. Any help would be highly appreciated. 🙂

[amitchandak · Accepted solution]

@Anonymous , First add an index column in power query  https://stackoverflow.com/questions/45715963/creating-an-index-column-for-power-bi

Post that in DAX create a new column

new date =
var _max = maxx(filter(Table, not(isblank([Date])), [index])
var _maxd = maxx(filter(Table, not(isblank([Date])), [Date])
return
if(not(isblank([Date])), [Date],_maxd + [Index]-_max)

[Anonymous]

OMG, it works, I cannot thank you enough for this. Thank you so much!