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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

+

addition

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

Table 3. Function Editor (logical operators) 

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.

/* Some sort of comment

about the function */

5 + 4

// Comment// begins a single line comment. Can be placed after an expression to make the rest of the line a comment.5 + 4 // A 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 and context variables. Tables 10-11 list the default available options. You can also create custom date ranges.

See further details about the use of date ranges and their relation to Time of Evaluation of functions and variables.

Table 10. Function Editor (Date range instances)

Date Range

Meaning

Current Time Step

The most recently updated value. "Current" starts from 0 in Time Step Date Range definition.

Current Iteration

Only applicable to Ordering with 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.

Current 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.

Current 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.

Previous 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.

Previous 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.

Previous 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

Previous Hundred Time Steps (set)

The set of values from the model for the previous 100 time steps.

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

Previous Seven Days (set)

For a daily 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 sum of the timestep values for each of the previous seven days.

Average($var) - finds the average of the previous seven day totals

Previous 30 Days (set)

For a daily model, this is the set of the values from the last 30 time steps. For a sub-daily model, this is the set of the sum of the timestep values for each of the previous 30 days.

Sum($var) - finds the sum of the previous 30 days

Previous 365 Days (set)

For a daily model, this is the set of the values from the last 365 time steps. For a sub-daily model, this is the set of the sum of the timestep values for each of the previous 365 days.

Max($var) - finds the maximum day from the previous 365 days

Built-in Functions for Data Sources and Probability of Exceedance (PoE)

There are four new built-in Functions:

GetDataPeriod

Gets data from a Data Source between the start and end dates. Data is returned as an array.

Example usage:

//Arguments are: Data Source (for files, Name.ColumnName), start year, start month, start day, end year, end month, end day
 GetDataPeriod("MyDataSource_csv.Column1"20001120201231)

//Returns an array of values in the units of MyDataSource_csv.Column1.

GetDataTimeSteps

 Gets data from a Data Source using a start date and the number of time steps. Data is returned as an array.

Example usage:

//Arguments are: Data Source (For files, name and column name), start year, start month, start day, number of time steps
GetDataTimeSteps("MyDataSource_csv.Column1"200011365)
//Returns an array of values in the units of MyDataSource_csv.Column1.

ProbabilityOfExceedanceFlow 

Gets the percentage value for the given flow from the probability of exceedance curve. This function is useful to calculate probability of exceedance (PoE) inflows to determine storage operating targets, spill assessments etc. For example, it calculates probability of exceedance (PoE) flow that is a time series (data source) or a modelled variable such as 95% probability of exceedance (PoE) inflows to a storage.

Example usage:

//Arguments are: Array of values, flow value (in the units of Flow_res_csv.Runoff)
ProbabilityOfExceedanceFlow(GetDataTimeSteps("Flow_res_csv.Runoff"200011365),1000)

The above function returns the percentage of flow values in the data source period from from 01/01/2000 for 365 days which are equal or above 1000 (the units of the data source and input threshold value must match).

//One can also use a modelled variable to provide the array of values

ProbabilityOfExceedanceFlow($Previous30DaysFlow,10)

ProbabilityOfExceedancePercentage 

Gets the flow value for the given percentage from the probability of exceedance curve.

Example usage:

//Arguments are: Array of values, percentage
ProbabilityOfExceedancePercentage(GetDataTimeSteps("Flow_res_csv.Runoff"200011365),20)

The above function returns flow value for which 20% of values in the "Flow_res_csv.Runoff" are equal or above.


Example model using built-in functions for data sources and probability of exceedance together

The example model as shown in the Figure 1 uses a combination of newly built-in functions 'ProbabilityOfExceedanceFlow' and 'GetDataPeriod' to return the percentage of flow values equal to or above a certain flow.

 Figure 1. Example model using built-in function 'ProbabilityOfExceedanceFlow'


For example, a function named '$PoE_Flow' -> ' ProbabilityOfExceedanceFlow(GetDataPeriod("$Variable2", 1990,1,1, 2000,12,31), 600)' is created, where '$Variable2' is a time series variable containing flow data from 1990 to 2000.  Once ran, the model returns a percentage value which shows the probability of exceedance of 600 ML in the $Variable2 (in this case 93.25%). In this function, 'GetDataPeriod' is used to get data from 1990 to 2000.

It is to be noted that if 'ProbabilityOfExceedanceFlow' is used, the Result Units must be 'percent' and if 'ProbabilityOfExceedancePercentage' is used, the units must be flow units (e.g. megalitre). 


Tip  for performance enhancement - if you have static inputs as above , its recommended to set the time of evaluation (ToE) to 'Start of Run' to significantly enhance the performance


One can also use modelled variables  as input arguments instead of a static variable (600 in this case) to return varying probability of exceedance (PoE) during the run. 

For example, the function, $PoE_Flow ->  ProbabilityOfExceedanceFlow(GetDataPeriod("$Variable2", 1990,1,1, 2000,12,31), $Function1) can be used to return the varying PoE over 1990 to 2000. In this case, $Function1>- sum($Variable1), where $Variable1 is a modelled variable with 'Date Range' from April to June and recurring. Therefore, '$PoE_Flow' returns the PoE of sum of flows from April to June every year in the data source $Variable2 from 1990 to 2000 and it will be varying over the simulation period.


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