> ## Documentation Index
> Fetch the complete documentation index at: https://docs.truemath.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Authoring tables

> Define a table-valued variable — its columns, per-column format, row labels, starting row index, and an optional default table.

A **table** variable holds a collection of values in rows and columns rather than a single number — an amortization schedule, a series of cash flows, a set of line items, a lookup grid. Whether a variable holds a table is determined by its value — produced by a calculation or supplied as input — not by its display type. The `table` display type (see [Defining variables](/authoring/defining-variables)) is how you get the table-specific display options: named columns, per-column formats, and row labels. A table value given a scalar display type such as `number` still renders as a table, but every cell takes that type's formatting — thousands separators, the configured decimal places — and the columns fall back to generic headers. This page covers the authoring side; for the underlying value model — how tables are written, stored, and combined — see [Tables](/math/types/tables).

## When to use a table

Use a table variable when a quantity is naturally many values rather than one: a payment broken out month by month, a list of material costs, a grid of rate-by-term lookups. A variable that holds a single value should stay a scalar `number`, `percent`, or `no_separator`.

## Rows versus columns

The authoring distinction that matters: **columns are defined, rows are data.** You name and format the columns when you author the variable; the rows are produced by a calculation or supplied as input, and there can be any number of them. Tables are **1-indexed** — the first row and column are index `1`. So you configure the shape across, not down.

## Configuring columns

Each column has:

* **A name** — the column's label.
* **A display type** — `number`, `percent`, or `no_separator`, the same scalar types a plain variable uses.
* **A decimal format** — `decimals_0` through `decimals_9`, or `decimals_float`, applied when the column's values are shown.

You also set the **starting row index** — the number shown as the label of the first row, like the row numbers down the side of a spreadsheet. It is a display indicator only and does not change how the table is indexed in equations, which is always 1-based. It is usually `1`; setting it to `0` is occasionally handy when displaying a cash-flow table whose initial flow is period 0 (`CF[0]`), for instance.

Columns have no unit field: each cell carries its own unit, supplied with the value, so the variable's own unit is empty (see [Tables as a stored value](/math/types/tables#as-a-stored-value)).

## Row labels

A table can optionally carry **row labels**, so its rows read by name rather than only by index — for example, labeling an amortization table's rows by month, or a cost breakdown's rows by line item. Row labels are a presentation aid; they name the rows without changing the values in them.

Row labels are an independent option: a table can have row labels with or without a [default table](#default-table), or none at all, but accessed and set in the default table view.

## Default table

A table variable can carry a **default table** — a complete table value used when a calculation provides none, the multi-value counterpart to a scalar [default value](/authoring/defining-variables#default-value-and-unit). A value supplied from a default is recorded with default [provenance](/concepts/provenance).

A default table is also independent of row labels: you can set a default table on its own, pair it with row labels, or use neither. A table variable with no default has none applied.

## Presenting a table as a chart

The same table variable can be displayed as a bar or pie chart instead of a grid — the chart is a presentation choice over the underlying table. See [Charts](/authoring/charts).