DAX evaluation order

[dicken]

hi,
can anyone point me in the direction of how DAX calculates, for example

I have the following measure ;

Pa salestotal:=SUM(pTaverage[units])

straight forward sum,

which I can then use ;
RTSALES:=VAR mdate = MAX(pTaverage[date])
VAR anser =
CALCULATE(SUMX(FILTER(ALL(pTaverage[date]),pTaverage[date] <= mdate ) , [Pa salestotal]) )
RETURN anser

but if I replace the measure at the end with ;

VAR mdate = MAX(pTaverage[date])
VAR anser =
CALCULATE(SUMX(FILTER(ALL(pTaverage[date]),pTaverage[date] <= mdate ) , SUM(pTaverage[units]) )
RETURN anser

it doen't work, I have tried wrapping in CALC, as measure have an implicit calculate but no good. but course if i placed the sum after Calculate and
then did the filtering it would.

CALCULATE(SUM(pTaverage[units])  ,FILTER(ALL(pTaverage[date]),pTaverage[date] <= mdatee ) )

CALCULATE(SUM(pTaverage[units]) ,FILTER(ALL(pTaverage[date]),pTaverage[date] <= mdatee ) )

 

[Matt Allington]

RTSALES :=
VAR mdate =
    MAX ( pTaverage[date] )
VAR anser =
        SUMX (
            FILTER (
                ALL ( pTaverage[date] ),
                pTaverage[date] <= mdate
            ),
            CALCULATE (
                SUM ( pTaverage[units] )
            )
        ) 
RETURN
    anser

The extra calc belongs inside the sumx around the sum()

 

[dicken]

RTSALES :=
VAR mdate =
    MAX ( pTaverage[date] )
VAR anser =
        SUMX (
            FILTER (
                ALL ( pTaverage[date] ),
                pTaverage[date] <= mdate
            ),
            CALCULATE (
                SUM ( pTaverage[units] )
            )
        )
RETURN
    anser

The extra calc belongs inside the sumx around the sum()

thanks again,

RD