Examples of Expressions

Type of Expression.


Example Syntax and Graph

Simple Number

Calculates a constant value in all scenario years


Simple Formula

Calculates a constant value in all scenario years

0.1 * 5970

Growth Rate

Calculates exponential growth over time from a Current Accounts value. NB: only valid in scenario expressions - not in Current Account expressions.



Calculates straight-line change between specified pairs of data years and values. An optional final parameter lets you specify an exponential growth rate after the last data year. The function can include any number of year/value pairs, which need to be entered in ascending chronological order. Notice that the value parameters in this function can themselves be specified as mathematical functions.

Interp(2000, 40, 2010, 65, 2020, 80)

Interp(2000, 0.9 * BaseYearValue, 2030, 0.7 * BaseYearValue)



Similar to the Interpolation function except that it calculates discrete changes between specified pairs of data years and values.

Step(2000, 300, 2005, 500, 2020, 700)


Calculates remaining value in one branch by subtracting values of all other neighboring branches from the function parameter. This function is useful for “share” branches, for example where you want to specify some branches as changing percentage share, and have one branch account for the remaining share.


Branch and Variable References

Any WEAP variable can be calculated as a function of another variable (with some restrictions)

Weaping River:Headflow * 0.25


Calculates a value in any given year based on its previous year's value and the rate of growth in another named branch, raised to the power of an elasticity.