/**
* Parses the provided expression and iterates over the {@link 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 {@link
* Ontology#NOMINAL} for strings, {@link Ontology#INTEGER} for integers, {@link Ontology#REAL} for
* reals, {@link Ontology#DATE_TIME} for Dates, and {@link Ontology#BINOMINAL} with values
* "true" and "false" for booleans. If the executing operator is defined,
* there will be a check for stop before the calculation of each example.
*
* @param exampleSet the example set to which the generated attribute is added
* @param name the new attribute name
* @param expression the expression used to generate attribute values
* @param parser the expression parser used to parse the expression argument
* @param resolver the example resolver which is used by the parser to resolve example values
* @param executingOperator the operator calling this method. <code>null</code> is allowed. If not
* null the operator will be used to check for stop
* @throws ProcessStoppedException in case the process was stopped by the user
* @throws ExpressionException in case parsing the expression fails
*/
public static Attribute addAttribute(
ExampleSet exampleSet,
String name,
String expression,
ExpressionParser parser,
ExampleResolver resolver,
Operator executingOperator)
throws ProcessStoppedException, ExpressionException {
// parse the expression
Expression parsedExpression = parser.parse(expression);
Attribute newAttribute = null;
// if != null this needs to be overridden
Attribute existingAttribute = exampleSet.getAttributes().get(name);
StringBuffer appendix = new StringBuffer();
String targetName = name;
if (existingAttribute != null) {
// If an existing attribute will be overridden, first a unique temporary name has to be
// generated by appending a random string to the attribute's name until it's a unique
// attribute name. After the new attribute is build, it's name is set the 'targetName'
// at the end of this method.
//
do {
appendix.append(RandomGenerator.getGlobalRandomGenerator().nextString(5));
} while (exampleSet.getAttributes().get(name + appendix.toString()) != null);
name = name + appendix.toString();
}
ExpressionType resultType = parsedExpression.getExpressionType();
int ontology = resultType.getAttributeType();
if (ontology == Ontology.BINOMINAL) {
newAttribute = AttributeFactory.createAttribute(name, Ontology.BINOMINAL);
newAttribute.getMapping().mapString("false");
newAttribute.getMapping().mapString("true");
} else {
newAttribute = AttributeFactory.createAttribute(name, ontology);
}
// set construction description
newAttribute.setConstruction(expression);
// add new attribute to table and example set
exampleSet.getExampleTable().addAttribute(newAttribute);
exampleSet.getAttributes().addRegular(newAttribute);
// create attribute of correct type and all values
for (Example example : exampleSet) {
if (executingOperator != null) {
executingOperator.checkForStop();
}
// bind example to resolver
resolver.bind(example);
// calculate result
try {
switch (resultType) {
case DOUBLE:
case INTEGER:
example.setValue(newAttribute, parsedExpression.evaluateNumerical());
break;
case DATE:
Date date = parsedExpression.evaluateDate();
example.setValue(newAttribute, date == null ? Double.NaN : date.getTime());
break;
default:
example.setValue(newAttribute, parsedExpression.evaluateNominal());
break;
}
} finally {
// avoid memory leaks
resolver.unbind();
}
}
// remove existing attribute (if necessary)
if (existingAttribute != null) {
AttributeRole oldRole = exampleSet.getAttributes().getRole(existingAttribute);
exampleSet.getAttributes().remove(existingAttribute);
newAttribute.setName(targetName);
// restore role from old attribute to new attribute
if (oldRole.isSpecial()) {
exampleSet.getAttributes().setSpecialAttribute(newAttribute, oldRole.getSpecialName());
}
}
// update example resolver after meta data change
resolver.addAttributeMetaData(
new AttributeMetaData(exampleSet.getAttributes().getRole(newAttribute), exampleSet, true));
return newAttribute;
}
