I want to display two charts on one page and have similar chart navigation and examination experience as iOS Apple Health app does. The issue is that Apple Heath has only one chart on the page but with two charts it becomes confusing how to properly use date navigation controls.
Have one date navigation control that controls two charts and when a user scrolls horizontally one of the charts - dates in the control change accordingly. Pros: More space is left for charts, one control reduces the clutter. Cons: While scrolling one chart it might get confusing why the other one scrolls.
Have two independent date navigation controls. Pros: Separate controls make scrolling and control of individual charts less confusing. Cons: Less space is left for charts, more cluttered UI.
Have one date navigation control and tabs that switch the chart. Pros: One chart at a time with one date navigation. Cons: Other chart is hidden, difficult to compare two charts.