Fill Missing Values

Data > Fill missing values... replaces empty or null cells in one column using a strategy you pick. Only empty/null cells are changed; existing values are left alone. Apply is a single undo step.

Strategies

Strategy	What it does
Mean	Fill with the column's average (numeric columns only).
Median	Fill with the middle value (numeric columns only).
Mode	Fill with the most common value.
Constant	Fill with a fixed value you type.
Forward fill	Copy the nearest non-empty value from above.
Backward fill	Copy the nearest non-empty value from below.

A strategy that doesn't fit the data (for example Mean on a text column) shows an inline error and changes nothing. The operation respects read-only mode.

Command line and assistant

Also available as octa --impute COL=STRATEGY (see the --impute reference) and as the fill_missing MCP / assistant tool.