An unrecorded observation and a measured zero mean different things. A line chart can blur that distinction if it draws an empty cell at zero or connects the surrounding points without explanation. Choose the display according to what the missing value means.

Use a copy of the report in desktop Excel for Windows. Inspect the actual source cell for the gap: this procedure concerns genuinely empty cells. A formula returning empty-looking text or an error needs its own check; do not assume every blank-looking cell has the same chart behaviour.

Choose the line chart’s missing-value treatment

Select the existing chart. On its Chart Design or Design tab, choose Select Data, then Hidden and Empty Cells. Under Show empty cells as, compare Gaps, Zero and Connect data points with line.

For an observation that was not recorded, Gaps can communicate the interruption without asserting a zero measurement. Connecting the surrounding points may be appropriate for an explicitly explained presentation choice, but it should not be mistaken for evidence about what happened during the missing interval.

The same dialog includes a separate choice for showing data in hidden rows and columns. Inspect that independently. Hiding a source row and leaving its value empty are different actions, even if both can make a chart appear to lose a point.

Use a real zero as the comparison

In a disposable copy of the chart’s source, use five consecutive category labels with values 6, 8, an empty cell, 7 and 0. Keep the category for the missing observation. With Gaps selected, inspect the interruption at the third category and the genuine zero at the fifth.

Read the chart as someone who has not seen the worksheet. Can they distinguish the missing observation from the recorded zero? Add a concise explanation in the report when that distinction affects interpretation.

Restore the real source values and review the finished chart at its delivery size. Check the category labels, the missing interval and any hidden-row setting after the final edit. Preserve the original observations rather than manufacturing zeroes or estimated values merely to make the line look complete.

Sources: Microsoft hidden and empty chart cells.