Expressions

This guide describes the use of expressions within the Low Emissions Analysis Platform (LEAP), explaining how mathematical formulae are used to specify variable values in the Analysis View for both historical data and future scenarios.

• Expressions in LEAP are mathematical formulae used to define variable values in the Analysis View. In Current Accounts, they define historical values at a branch, while in scenarios, they determine how a variable changes from the First Scenario Year to the End Year of the study period.
• LEAP provides several tools for editing expressions, including direct typing in the Analysis View, an Expression Builder tab, a pop-up selection box for common functions (Interpolation, Growth, End-Year, and Remainder), a Time-Series Wizard (Ctrl+T), a Function Wizard (Ctrl+F), and a Branch/Variable Wizard (Ctrl+B).
• To reduce data entry, LEAP uses a scenario hierarchy where expressions are inherited from parent (ancestor) scenarios. The software uses color coding in the Analysis View to indicate the source of an expression: purple for explicit entry, black for inheritance from another scenario or region, green for inheritance from another region in multi-region sets, silver for default expressions, and red italics for errors.
• Users can create models by referencing other variables within expressions. These include data variables (specified directly in Analysis View) and results variables (calculated internally by LEAP, such as total emissions or costs). Generally, results variables can only be referenced for previous years using the PrevYearValue function, except when specifying calculated Indicator variables.
• The Expression Elaboration feature provides a tab in the Analysis View that details the branches and variables a current expression depends on, as well as which branches, variables, and scenarios depend on the current branch.

APA

Stockholm Environment Institute (n.d.). Expressions. https://cdn.leap.sei.org/Help24/Concepts/Expressions.htm

Chicago

Stockholm Environment Institute. Expressions. n.d. https://cdn.leap.sei.org/Help24/Concepts/Expressions.htm.

Wikipedia

{{cite report |author=Stockholm Environment Institute |title=Expressions |url=https://cdn.leap.sei.org/Help24/Concepts/Expressions.htm |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{stockholmenvironmentinstitutendexpressions, author = {{Stockholm Environment Institute}}, title = {{Expressions}}, institution = {Stockholm Environment Institute}, url = {https://cdn.leap.sei.org/Help24/Concepts/Expressions.htm}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }