Note: This is documentation for version 4.11 of Source. For a different version of Source go to the Space Directory.
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# Available functions, operators, variables and date ranges

Built-in functions are predefined formulae that perform calculations that usually depend on the arguments you supply as parameters. They can be entered manually or by using the pull down menu at the top of the Function Editor. The available operators and functions are summarised in Tables 1-7. Examples of function use are shown in Table 8. Available built-in variables are defined in Table 9. Default date ranges are summarised in Tables 10 and 11

Note: Any characters not listed on this page are considered invalid, and will result in an error at parse time and run time.

## Operators

###### Table 1. Function Editor (Arithmetic operators)

Operator

Meaning

Example

Result

+

10 + 5

15

-

subtraction; negation

10 - 5 = 5 or 10 + (-5)

5

*

multiplication

10 * 5

50

/

division

10 / 5

2

** or ^

power/exponentiation

10**5 or 10^5

100000

( )

influence order of evaluation

5 * (10 + 5)

75

###### Table 2. Function Editor (Comparison operators)

Operator

Meaning

Example

Result

Equivalent to

>

greater than

10 > 5

true

<

less than

10 < 5

false

>=

greater than or equal

10 >= 5

true

<=

less than or equal

10 <= 5

false

=

equal

10 = 5

false

<>

not equal

10 <> 5

true

~>

greater than with tolerance

1 ~> 0.999999999

false

ABS(1 - 0.999999999) <= 1e-8 AND 1 > 0.999999999

~<

less than with tolerance

1 ~< 0.999999999

false

ABS(1 - 0.999999999) <= 1e-8 AND 1 < 0.999999999

~>=

greater than or equal with tolerance

1 ~>= 0.99999999

true

ABS(1 - 0.999999999) <= 1e-8 OR 1 > 0.999999999

~<=

less than or equal with tolerance

1 ~<= 0.99999999

true

ABS(1 - 0.999999999) <= 1e-8 OR 1 < 0.999999999

~=

equal with tolerance

1 ~= 0.99999999

true

ABS(1 - 0.999999999) <= 1e-8

Note - the tolerance set for the ~ variants is equal to 1e-8 (the same for many comparisons used within Source).

## Functions

Operator

Meaning

Example

Result

OR

or

false OR true

true

AND

and

false AND true

false

NOT

not

NOT false

true

###### Table 4. Function Editor (General mathematical functions)

Function

Meaning

Example use

EXP

Returns e raised to the power of a given number

EXP(number)

LOG10

Returns the base-10 logarithm of a number

LOG10(number)

LN

Returns the natural logarithm of a number

LN(number)

ABS

Returns the absolute value of a number

ABS(number)

SQRT

Returns a positive square root

SQRT(number)

MOD

Returns the remainder from division

MOD(number,divisor)

ROUND

Rounds a number to the nearest integer

ROUND(number)

INT

Rounds the number down to the nearest integer

INT(number)

###### Table 5. Function Editor (Statistical functions)

Function

Meaning

Example use

AVERAGE

Returns the average of its arguments

AVERAGE(variable_name)

COUNT

Counts how many numbers are in the list of arguments

COUNT(variable_name)

COUNTIF

Counts how many numbers in the list of arguments satisfy the expression

COUNTIF(variable_name,expression)

MAX

Returns the maximum value in a list of arguments

MAX(variable_name) or MAX(number,number)

MEDIAN

Returns the median of its arguments

MEDIAN(variable_name)

MIN

Returns the minimum value in a list of arguments

MIN(variable_name) or MIN(number,number)

STDEV

Estimates standard deviation based on a sample

STDEV(variable_name)

SUM

Adds all the values of a modelled variable that has a date range

SUM(variable_name)

###### Table 6. Function Editor (Trigonometric functions)

Function

Meaning

Example use

ARCCOS

Returns the inverse cosine of a number

ARCCOS(number)

ARCSIN

Returns the inverse sine of a number

ARCSIN(number)

ARCTAN

Returns the inverse tangent of a number

ARCTAN(number)

COS

Returns the cosine of a number

COS(number)

SIN

Returns the sine of a number

SIN(number)

TAN

Returns the tangent of a number

TAN(number)

###### Table 7. Function Editor (Miscellaneous functions)

Function

Meaning

Example use

IF

Specifies a logical test to perform

IF(logical_test,value_if_true,value_if_false)

LOOKUP

Looks up the Y-value corresponding to an X-value via a piecewise linear variable or looks up the return value that correspond to X and Y values via a bilinear variable. Both lookups use linear interpolation.

LOOKUP(variable_name, number)

LOOKUP(variable_name, x, y)

N1

Returns 1 if the number is less than zero, 0 otherwise

N1(number)

P1

Returns 1 if the number is greater than zero, 0 otherwise

P1(number)

PI

Returns the mathematical constant π to 14 decimal places

PI()

/* Comment *//* begins a comment and */ ends a comment. Comments can go over multiple lines.

5 + 4 /* Some sort of comment about the function*/

###### Table 8. Sample expressions using functions

Expression

Result

Expression

Result

Expression

Result

Average(\$var1)

3

Median(\$var1)

3

Lookup(\$var1,13.5)

2.5

Lookup(\$var1,14)

3

Count(\$var1)

5

Max(\$var1)

5

Min(\$var1)

1

Sum(\$var1)

15

Stdev(\$var1)

1.58113883

Where: \$var1 is the piecewise linear relationship {(12, 1), (13, 2), (14, 3), (15, 4), (16, 5)}

## Variables

###### Table 9. Function Editor (Built-in variables)

Variable

Meaning

\$Now.Year

Returns the 4-digit year of the current time-step

\$Now.Month

Returns the month of the current time-step (range: 1...12)

\$Now.Day

Returns the day of the current time-step (range: 1...31)

\$Now.Hour

Returns the hour of the current time-step (range 0...23)

\$Now.DaysInMonthReturns the number of days in the month for the current time-step (range, 28..31)
\$Now.DayOfYearReturns the current day in the year for the current time-step (range, 1, 366)
\$Start.YearReturns the 4-digit year of the simulation start date
\$Start.MonthReturns the month of the start of simulation date(range: 1...12)
\$Start.DayReturns the day of the simulation start date (range: 1...31)
\$Start.HourReturns the hour of the simulation start date (range 0...23)
\$Start.DaysInMonthReturns the number of days in the month for the simulation start date (range, 28..31)
\$Start.DayOfYearReturns the current day in the year for the simulation start date(range, 1, 366)
\$End.YearReturns the 4-digit year of the simulationend date
\$End.MonthReturns the month of the simulation end date (range: 1...12)
\$End.DayReturns the day of the simulation end date (range: 1...31)
\$End.HourReturns the hour of the simulation end date (range 0...23)
\$End.DaysInMonthReturns the number of days in the month for the simulation end date (range, 28..31)
\$End.DayOfYearReturns the current day in the year for the simulation end date (range, 1, 366)
\$ActiveInputSet

Returns the simulation input set. Can be used in statements like if(\$ActiveInputSet = "Wet", 15, 10). It is also possible to reference a child scenario input set, see Referencing scenario input sets in functions.

## Default date ranges

Source provides a set of default date ranges that allow you to specify values to use for modelled variables. Tables 10-11 list the default available options. You can also create custom date ranges.

###### Table 10. Function Editor (Date range instances)

Date Range

Meaning

Current Time Step

The most recently updated value.

Current Iteration

Only applicable to NetLP. The value updated during the last iteration of the solver.

Current Day

For a sub-daily model, it is the sum of the values for the current day. For a daily model, this is a synonym for Current Time Step.

This Month

For a sub-monthly model, it is the sum of the values for the current month. For a monthly model, this is a synonym for Current Time Step.

This Calendar Year

For a sub-yearly model, it is the sum of the values for the current calendar year. For a yearly model, this is a synonym for Current Time Step.

Last Time Step

The value of the variable at the completion of the previous iteration of the model.

Previous Day

For a sub-daily model, it is the sum of the values for the previous day. For a daily model, this is a synonym for Last Time Step.

Last Month

For a sub-monthly model, this is the sum of the values for the previous month. For a monthly model, this is a synonym for Last Time Step.

Last Calendar Year

For a sub-yearly model, it is the sum of the values for the previous calendar year. For a yearly model, this is a synonym for Last Time Step.

###### Table 11. Function Editor (Date range sets)

Date Range

Meaning

Example of use

Last Hundred Time Steps

The set of values from the model for the previous 100 iterations.

Lookup(\$var,35)
(finds 35th value)

Last Seven Days

For a daily or monthly model, this is the set of the values from the last seven time steps. For a sub-daily model, this is the set of the average daily values for each of the previous seven days.

Average(\$var)

Previous 30 Days

For a daily or monthly model, this is the set of the values from the last 30 time steps. For a sub-daily model, it is the set of the average daily values for each of the previous 30 days.

Average(\$var)

Last 365 Days

For a daily or monthly model, this is the set of the values from the last 365 time steps. For a sub-daily model, it is the set of the average daily values for each of the previous 365 days.

Average(\$var)

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