Calculating Weighted IRR using XIRR properly

Ashish_Mathur Indeed it`s quite a complex challenge, it is simply a try to calculate weighted IRR (against Capex) of 2 subsets of the data and comparing them while applying multiple filters.

I was able to resolve it and I hope the code itself describes better the solution:

WAIRR Change test =

//calculations for IRR of baseline only:
var tableIRRbase0=SUMMARIZE(CALCULATETABLE(
'result',KEEPFILTERS('result'[Baseline/Change]="Baseline"),ALL('result'[Source Fiscal Year])),
'result'[Asset Scenario ID],'result'[Source Parameter],
"IRR",XIRR(FILTER('result','result'[Impacted Parameter]="Cashflow"&&'result'[Baseline/Change]="Baseline"),[Value],'result'[Impacted Date]),
"Capex",
SUMX(FILTER(('result'),'result'[Impacted Parameter]="Capex"&&'result'[Baseline/Change]="Baseline"),'result'[Value])
)
var tableIRRbase1= ADDCOLUMNS(tableIRRbase0,"WIRR",[Capex]*[IRR])
var tableIRRbase2=ADDCOLUMNS(tableIRRbase1,"C",[WIRR]/CALCULATE(SUMX(tableIRRbase1,[Capex])))

//calculations for IRR of baseline and change:
var tablechange0= SUMMARIZE(
UNION(
CALCULATETABLE('result',KEEPFILTERS('result'[Baseline/Change]="Baseline"),ALL('result'[Source Fiscal Year])),
CALCULATETABLE('result',KEEPFILTERS('result'[Baseline/Change]="Change"),KEEPFILTERS('result'[Stress Direction]="Positive"))),
'result'[Asset Scenario ID],'result'[Source Parameter],
"IRR",XIRR(FILTER('result','result'[Impacted Parameter]="Cashflow"),[Value],'result'[Impacted Date]),
"Capex",
SUMX(FILTER(('result'),'result'[Impacted Parameter]="Capex"),'result'[Value])
)

var tableIRRchange1= ADDCOLUMNS(tablechange0,"WIRR",[Capex]*[IRR])
var tableIRRchange2=ADDCOLUMNS(tableIRRchange1,"C",[WIRR]/CALCULATE(SUMX(tableIRRchange1,[Capex])))

//Returning the required difference calculation
return (SUMX(tableIRRchange2,[C])-SUMX(tableIRRbase2,[C]))/SUMX(tableIRRbase2,[C])