Which type of analytics line should be used if the line must equal the result of a DAX measure returning a consistent single value?

Using a constant line is appropriate when you want to represent a value in your visual that remains unchanged and is equivalent to a specific DAX measure that consistently returns the same value. The constant line serves as a reference line across the visual, allowing viewers to quickly understand the context of data points in relation to this fixed benchmark.

In cases where a measure returns a constant value, the constant line effectively conveys this information without any variations, ensuring clarity in the visual representation. This makes it an ideal choice for illustrating goals, thresholds, or averages that do not fluctuate over time.

The other types of lines, such as average, max, or min lines, are inherently designed to depict dynamic values that can change based on the data being analyzed. These lines adjust according to the data set they are referencing and would not accurately reflect a stable value derived from a consistent DAX measure. Therefore, for a scenario requiring a line that consistently mirrors a specific DAX measure's single output, the constant line is the best option.