Countif for specific customers

Hey,

it seems this measure

NoOfPurchasesInFirstYear = 
CALCULATE(
SUMX(
	'Purchases'
	,var customer = 'Purchases'[Customer]
	var yearoffirstpurchase = YEAR('Purchases'[PurchaseDate])
	return
		COUNTROWS(
			FILTER(
				ALL('Purchases')
				,Purchases[Customer] = customer 
				&& YEAR('Purchases'[PurchaseDate]) = yearoffirstpurchase
			)
		)
	)
,'Purchases'[IsFirstPurchase] = "Yes"
)

creates what you are looking for

Here is sample data if you want to recreate my example

PurchaseDate	Customer	IsFirstPurchase
2017-01-07	C1	No
2017-07-09	C1	No
2016-08-02	C1	No
2016-06-01	C1	Yes
2017-01-07	C2	Yes
2017-07-09	C2	No
2016-07-04	C1	No

Hope this is what you are looking for

Be my guest.

The result

The Measure

SumOfPurchasesInFirstYear = 
CALCULATE(
SUMX(
	'Purchases'
	,var customer = 'Purchases'[Customer]
	var yearoffirstpurchase = YEAR('Purchases'[PurchaseDate])
	return
		CALCULATE(SUM(Purchases[Amount]),
			FILTER(
				ALL('Purchases')
				,Purchases[Customer] = customer 
				&& YEAR('Purchases'[PurchaseDate]) = yearoffirstpurchase
			)
		)
	)
,'Purchases'[IsFirstPurchase] = "Yes"
)

The enhanced sample data (sligthly enhanced :-))

Cheers