Variables

A variable is a named value within a domain — a home price, an interest rate, a monthly payment. Variables are what activities relate, and what you provide and receive when you run a calculation.

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What a variable has

A variable is defined in a domain and takes on a value when a calculation runs. As defined, a variable has:

• A key — an identifier, unique within the domain. You reference a variable by its key when you provide or solve for it (see Input formats), and the API returns it on each variable.
• A title and description — human- and agent-readable labels.
• A type and display format — how the value is interpreted and shown (see below).
• A default value — an optional value and unit used when none is provided.

When a calculation runs, each variable also has:

• A value — the number or table it currently holds, with its unit where applicable; the unit travels with the value (see Units and precision).
• Provenance — where that value came from: user-stated, calculated, carried forward, or a default. See Provenance.

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Types and display formats

A variable holds one of TrueMath’s value types — a scalar number, a unit number, or a table — and specifies how it should be displayed:

• number — a plain number, shown with thousands separators and a chosen decimal format. A monetary amount is a number whose unit is a currency (for example USD).
• percent — a rate shown as a percentage.
• no_separator — a number shown without thousands separators (for example, a year).
• table — a collection of values with named rows and columns.
• bar_chart / pie_chart — a table presented as a chart.

For how values combine across types, see Combining types. For authoring variables, see Defining variables.