com.rapidminer.tools.math.function
Class ExpressionParser

java.lang.Object
  com.rapidminer.tools.math.function.ExpressionParser

public class ExpressionParser
extends java.lang.Object

This class can be used as expression parser in order to generate new attributes. The parser constructs new attributes from the attributes of the input example set.

The following operators are supported:

• Addition: +
• Subtraction: -
• Multiplication: *
• Division: /
• Power: ^
• Modulus: %
• Less Than: <
• Greater Than: >
• Less or Equal: <=
• More or Equal: >=
• Equal: ==
• Not Equal: !=
• Boolean Not: !
• Boolean And: &&
• Boolean Or: ||

The following log and exponential functions are supported:

• Natural Logarithm: ln(x)
• Logarithm Base 10: log(x)
• Logarithm Dualis (Base 2): ld(x)
• Exponential (e^x): exp(x)
• Power: pow(x,y)

The following trigonometric functions are supported:

• Sine: sin(x)
• Cosine: cos(x)
• Tangent: tan(x)
• Arc Sine: asin(x)
• Arc Cosine: acos(x)
• Arc Tangent: atan(x)
• Arc Tangent (with 2 parameters): atan2(x,y)
• Hyperbolic Sine: sinh(x)
• Hyperbolic Cosine: cosh(x)
• Hyperbolic Tangent: tanh(x)
• Inverse Hyperbolic Sine: asinh(x)
• Inverse Hyperbolic Cosine: acosh(x)
• Inverse Hyperbolic Tangent: atanh(x)

The following statistical functions are supported:

• Round: round(x)
• Round to p decimals: round(x,p)
• Floor: floor(x)
• Ceiling: ceil(x)

The following miscellaneous functions are supported:

• Average: avg(x,y,z...)
• Minimum: min(x,y,z...)
• Maximum: max(x,y,z...)

The following miscellaneous functions are supported:

• If-Then-Else: if(cond,true-evaluation, false-evaluation)
• Absolute: abs(x)
• Square Root: sqrt(x)
• Signum (delivers the sign of a number): sgn(x)
• Random Number (between 0 and 1): rand()
• Modulus (x % y): mod(x,y)
• Sum of k Numbers: sum(x,y,z...)
• Binomial Coefficients: binom(n, i)
• Number to String: str(x)
• String to Number: parse(x)
• Substring: cut(x, start, len)
• Retrieving parameter value: param(operator name, parameter name)

Beside those operators and functions, this operator also supports the constants pi and e if this is indicated by the corresponding parameter (default: true). You can also use strings in formulas (for example in a conditioned if-formula) but the string values have to be enclosed in double quotes.

Please note that there are some restrictions for the attribute names in order to let this operator work properly:

• If the standard constants are usable, attribute names with names like "e" or "pi" are not allowed.
• Attribute names with function or operator names are also not allowed.
• Attribute names containing parentheses are not allowed.

If these conditions are not fulfilled, the names must be changed beforehand, for example with the ChangeAttributeName operator.

Examples:
a1+sin(a2*a3)
if (att1>5, att2*att3, -abs(att1))

Author:

Ingo Mierswa

Constructor Summary

ExpressionParser(boolean useStandardConstants)

ExpressionParser(boolean useStandardConstants, Process process)
This constructor allows additional functions if called within a process.

Method Summary

void	addAttribute(ExampleSet exampleSet, java.lang.String name, java.lang.String function) Iterates over the ExampleSet, interprets attributes as variables, evaluates the function and creates a new attribute with the given name that takes the expression's value.
void	addMacro(MacroHandler macroHandler, java.lang.String name, java.lang.String function)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ExpressionParser

public ExpressionParser(boolean useStandardConstants)

ExpressionParser

public ExpressionParser(boolean useStandardConstants,
                        Process process)

This constructor allows additional functions if called within a process.

Method Detail

addMacro

public void addMacro(MacroHandler macroHandler,
                     java.lang.String name,
                     java.lang.String function)
              throws GenerationException

Throws:

GenerationException

addAttribute

public void addAttribute(ExampleSet exampleSet,
                         java.lang.String name,
                         java.lang.String function)
                  throws GenerationException

Iterates over the ExampleSet, interprets attributes as variables, evaluates the function and creates a new attribute with the given name that takes the expression's value. The type of the attribute depends on the expression type and is Ontology.NOMINAL for strings, Ontology.NUMERICAL for reals and complex numbers and Ontology.BINOMINAL with values "true" and "false" for booleans.

Throws:

GenerationException