If there are some gaps in source data for the chart, by default, Excel does not display them on the chart, and this looks odd. Excel offers a useful feature to display interpolated values instead of gaps in the chart. In addition, Excel allows you to process data with #N/A errors as empty cells.
Excel allows you to create charts and diagrams from different data sets, even those that contain hidden or empty cells. However, sometimes you may see unexpected results. For example, if there are hidden cells in the chart data, by default, Excel ignores such data and doesn't display the corresponding chart elements. You can easily force Excel to handle hidden data.
Usually, horizontal lines are added to a chart to highlight a target, threshold, limits, base, average, or benchmark. These lines, for example, can help control if a process is behaving differently than usual. Excel allows you to add a vertical line to an existing chart in several different ways, e.g., by calculating line values for a scatter, line, or column chart, but using error bars is the easiest way to add a vertical line to a chart: