I then created a calculated column on the data table named GT, which stored the values of this measure. The data was unpivoted, so each row has a single measurement and a single date. That ensured that the measure wasn’t blank.
I took this column and used the VALUES() function to create a new table, MeasureValues.
MeasureValues = VALUES(Data[GT])
This gave me a table of all of the measure values of the data. In this case it was just “Y” and “N”, but it could have been any number of different values, depending on how they defined the original measure.