EMK:Formulae and Functions

Formulae can be entered as substitutes for specific values into most fields in EMarket to control the derivation of variable values at run time. A formula can contain any combination of:

• Constants
• Variables
• Operators
• Entities and Traits
• Functions

Constants

Constants can be:

• Numbers: Integers or Reals (e.g. 1, 2.5, -3), they can also be entered in scientific notation e.g. '3E+10'.
• Strings: Written inside double quotes e.g. "A Node"
• Dates: Must be enclosed in single quotes e.g '1/3/2004' or '14 April 2005'

Warning: The format for entering dates should compatible with the computer's local date (locality) setting

Variables

Variables can be regarded as user-defined Entity.Traits which can be defined in the Volatility Matrix or the Schedule. Previously defined variables can be used in formulae.

Note: EMarket provides a 'system' variable the user need not define: 'DateTime' which is of type 'Date' and gives the current simulation date as the model runs.

Operators

Operators are all pre-defined in EMarket. Their purpose is to separate a formula into parts that are then combined to give a single value.

The following operators are shown in descending order of precedence.

Operator	Meaning	Example	Parameter Type	Return Type
\	Integer Division	3\2 = 1	Real; Int	Int
%	Modulus	7%5 = 2	Real; Int	Int
/	Division	3/2 = 1.5	Real; Int	Real
*	Multiplication	5*4.2 = 21	Real; Int	Real
-	Subtraction	7-3.2 = 3.8	Real; Int	Real
+	Addition	3.5+1.5 = 5	Real; Int	Real

Functions

Functions provide a powerful mechanism for deriving field and variable data values from input parameters.

A function has the form FunctionName(Parameter1, Parameter2, ...)

An operator is used in a Function in the following form: <Parameter1>Operator<Parameter2>.

EMarket provides the following function types:

• Arithmetic functions
• Logic functions
• Run information functions
• Time functions
• Other functions

Note: Logic operators and functions evaluate to one for a result that is true (for example 6 = 6), and zero for false.

Arithmetic Functions

The following table lists EMarket's Arithmetic functions:

Function	Purpose	Parameters (Description, Type)	Return Type	Example	Result
Sqrt	Square root of a number	Number, Integer or Real	Real	Sqrt(546.94)	23.387
Abs	Absolute value of a number	Number, Integer or Real	Real	Abs(-19.1)	19.1
Int	Integer portion of a number	Number, Integer or Real	Integer	Int(45.786)	45
Sum	Total value of numbers in an array	Value Array (Exclude Value), Integer or Real	Real	Sum(Node.Price)
Max	Maximum value of numbers in an array, optionally excluding values with value over an exclude value	Value Array (Exclude Value), Integer or Real	Real	Max(Generator.Generation)
Min	Minimum value of numbers in an array	Value Array (Exclude Value), Integer or Real	Real	Min(Generator.Generation)
StdDev	Standard deviation of numbers in an array	Value Array (Exclude Value), Integer or Real	Real	StdDev(Generator.Generation)
Avg	Average value of numbers in an array	Value Array (Exclude Value), Integer or Real	Real	Avg(Generator.Generation)
WgtAvg	Average of numbers in an array, weighted by numbers in another array	Value Array (Weights Array), Integer or Real	Real	WgtAvg(Generator.Generation,Generator.Cost)
Choke	Returns a collared value (i.e. the value of the referenced variable is returned if it falls within the specified range otherwise the relevant minimum or maximum value is returned)	Number, Integer or Real	Real	Choke(500,200,Generator.Generation)

Logic Functions

The following table lists EMarket3's Logic functions:

Operator	Purpose	Parameters (Description, Type)	Return Value	Example	Result
=	Whether two numbers are Equal	2 numbers, Integer or Real	0 or 1	5 = 6	0
<	Whether first number is less than the second	2 numbers, Integer or Real	0 or 1	-2 < 7	1
>	Whether first number is Greater than the second	2 numbers, Integer or Real	0 or 1	9 > 7	1
AND	Whether two numbers are both non-zero	2 numbers, Integer or Real	0 or 1	And(6=6,4<3)	0
OR	Whether either of two numbers are non-zero	2 numbers, Integer or Real	0 or 1	OR(3<5, 2>3)	1
Between	Whether a number is between two limits	Number: lower limit; upper limit, Integer, real or date	0 or 1	Between(5.7,9.7)	0

Run Information Functions

The following table lists EMarket's Run information functions:

Function	Purpose	Parameters	Return Type
Date	Date of current Tick	None	Date
TP	TP number of current Tick	None	Integer
Version	The position of a Run in a Batch sequence. For first Run, Version is zero.	None	Integer

Time Functions

The following table lists EMarket's Time functions:

Function	Purpose	Parameters (Description, Type)	Return Type	Example	Result
GetDate	Converts a date to a day number	Date, Date	Integer	GetDate('1/4/2004')
hh	Gets the half hourly TP from a date	'DateTime'	Integer	hh(DateTime)
4h	Gets the number of the block of 4 hourly trading periods for a given date (e.g. 1 = TP 1-8)	'DateTime'	Integer	4h(DateTime)
6h	Gets the number of the block of 6 hourly trading periods for a given date (e.g. 0 = TP 1-12)	'DateTime'	Integer	6h(DateTime)
DOW	Gets the weekday for a date, 0 = Sunday	Date, Date	Integer	Dow('14/6/2004')	1
WO	Whether a date is a week day rather than a weekend or holiday, 1 = Weekend; 0 = Weekday	Date, Date	0 or 1	WO('13/6/2004')	1
WODN	0=Week Night(WN); 1=Week Day(WD); 2=Other Night(ON); 3=Other Day(OF)	Date (and time), Date	0 to 3	WODN('1/5/2004 22:00')	3
WODN6	0=Week Night(WN); 1=Week Day(WD); 2=Other Night(ON); 3=Other Day(OF). Using A night period running from Midnight to 6am (not to 8am as in WODN)	Date (and time), Date	0 to 3	WODN6('1/5/2004 22:00')	3
Month	Gets the month from a date, 0 = January	Date, Date	0 to 11	Month('1/5/2004')	4
WeekOfYear	Gets the week from a date, 0 = 1st full week in April	Date, Date	0 to 51	WeekOfYear('1/5/2004')	????
DateDiff	Calculates the number of days between two date/times	(Date 1, Date2), Dates	Real	DateDiff('1/5/2004', '5/5/004')	4
DateSeq	Gets the position of a required date within a list of ordered dates	(Date required, Lists of dates), Dates	Integer	DateSeq('5 / 4 / 2004', '1 / 4 / 2004', '2 / 4 / 2004', '3 / 4 / 2004', '4 / 4 / 2004', '5 / 4 / 2004')	5
TimeSeries	Given a date ordered sequence of values, finds the value for a required date	List of (value, last date applies), Real	Real	TimeSeries(735 , ' 1/04/2004 ', 760 , ' 1/04/2005 ', 840)