Currently, the Graph item ignores missing data points and always connects data points which have values. According to the "Displaying Missing Values and Incomplete Periods in Time Series" paper (https://www.perceptualedge.com/articles/visual_business_intelligence/missing_values_and_incomplete_periods_in_time_series.pdf) this approach of ignoring missing values is not recommended. The preferred approach (with gaps for missing values) is described in detail in the paper.