fill

Fills missing values in selected columns using the last non-missing value (down/LOCF) or a constant value.

Behavior:

• Down (LOCF): By default, missing values are replaced with the most recent non-missing value in the same column.
• Constant: If --value / -v is provided, missing values are replaced with this constant string.
• Missing Definition: A value is considered “missing” if it matches the string provided by --na (default: empty string).
• Filling is stateful across file boundaries when multiple files are provided.

Input:

• Reads from files or standard input.
• Files ending in .gz are transparently decompressed.

Header behavior:

• Supports --header / -H and --header-hash1 modes.
• When using header mode with multiple files, only the header from the first file is written; headers from subsequent files are skipped.

Field syntax:

• Use -f / --field to specify columns to fill.
• Columns can be specified by 1-based index or, if -H is used, by header name.
• Run tva --help-fields for a full description shared across tva commands.

Output:

• By default, output is written to standard output.
• Use --outfile to write to a file instead.

Examples:

1. Fill missing values in column 1 downwards tva fill -H -f 1 data.tsv

2. Fill missing values in columns ‘category’ and ‘type’ downwards tva fill -H -f category -f type data.tsv

3. Fill missing values in column 2 with “0” tva fill -H -f 2 -v "0" data.tsv

4. Treat “NA” as missing and fill downwards tva fill -H -f 1 --na "NA" data.tsv