Dynamic Comparison Between Periods using Parameter

Hi markzuev96 ,

Looking at your DAX, the "can't determine a single value" error usually happens when your parameter table or date selections are returning multiple values instead of single ones.

Most likely culprits:

Parameter selection issue: Your SELECTEDVALUE(ComparisonType[Comparison]) is probably returning BLANK() sometimes, which means either no comparison type is selected or multiple ones are selected. Add some debugging:

VAR ComparisonType = 
    IF(
        ISBLANK(SELECTEDVALUE(ComparisonType[Comparison])), 
        "Previous Period", -- default value
        SELECTEDVALUE(ComparisonType[Comparison])
    )

Date filter context problems: When there's no clear date selection, MIN(DateTable[Date]) and MAX(DateTable[Date]) might be acting weird. Try this:

VAR SelectedStart = 
    IF(
        ISFILTERED(DateTable[Date]),
        MIN(DateTable[Date]),
        BLANK()
    )
VAR SelectedEnd = 
    IF(
        ISFILTERED(DateTable[Date]),
        MAX(DateTable[Date]),
        BLANK()
    )

Add an early exit:

-- Right after your date variables
RETURN
IF(
    ISBLANK(SelectedStart) || ISBLANK(SelectedEnd) || ISBLANK(ComparisonType),
    BLANK(),
    -- rest of your calculation here
)

Quick test: Put your measure in a card visual with no filters applied. If it shows the error, then it's definitely a parameter/context issue.

The error usually shows up when users haven't made proper selections yet, or when the report first loads. Adding those validation checks should fix it.

Try the parameter default value fix first - that's usually the main culprit.

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