Formula Modal
This article explains the Formula modal in Model Reef.
You will learn:
How to open and use the Formula modal.
Which operators and references are allowed.
How validation and previews help you avoid mistakes.
Allowed operators and structure
The formula engine is arithmetic only.
You can use:
Addition:
a + bSubtraction:
a - bMultiplication:
a * bDivision:
a / bParentheses:
(a + b) * c
You cannot use:
IF, AND, OR or other logical operators.
Conditional expressions.
Text functions.
References to individual cells or positions.
Every formula you write is applied as a vector across all periods, not one period at a time.
Selecting inputs from sidebars
The Formula modal usually shows sidebars with:
Variables, grouped by branch and category.
Drivers, grouped by type.
Sometimes categories or aggregated series.
You can click to insert items into the formula instead of typing names manually. This avoids spelling errors and keeps formulas consistent with the rest of the model.
Preview and validation
As you edit the formula, Model Reef:
Checks that the syntax is valid.
Flags errors such as missing brackets or unknown names.
Provides a preview of the resulting time series so you can see whether the shape looks correct.
If there is a validation error, the variable will not update until you correct the formula.
Impact of formulas on statements
Formulas define the underlying time series for a variable. Once the formula is accepted:
The variable's P&L impact follows its type and timing settings.
Balance sheet entries such as receivables, payables, assets or loans are updated.
Cashflow Statement and Cash Waterfall flows are recalculated.
Formulas never place values directly on statements. They always work through the variable and timing engine.
Best practices
When writing formulas:
Keep them as simple as possible and push complexity into drivers where you can.
Use clear names for variables and drivers so formulas are self explanatory.
Avoid duplicating logic across many variables if it can be centralised in a driver or Data Library entry.
Document unusual formulas with notes in the Variable Editor.
This keeps the model easier to maintain and review.
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