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Class weka.core.Instance
java.lang.Object
|
+----weka.core.Instance
- public class Instance
- extends Object
- implements Copyable, Serializable
Class for handling an instance. All values (numeric, nominal, or
string) are internally stored as floating-point numbers. If an
attribute is nominal (or a string), the stored value is the index
of the corresponding nominal (or string) value in the attribute's
definition. We have chosen this approach in favor of a more elegant
object-oriented approach because it is much faster.
Typical usage (code from the main() method of this class):
...
// Create empty instance with three attribute values
Instance inst = new Instance(3);
// Set instance's values for the attributes "length", "weight", and "position"
inst.setValue(length, 5.3);
inst.setValue(weight, 300);
inst.setValue(position, "first");
// Set instance's dataset to be the dataset "race"
inst.setDataset(race);
// Print the instance
System.out.println("The instance: " + inst);
...
All methods that change an instance are safe, ie. a change of an
instance does not affect any other instances. All methods that
change an instance's attribute values clone the attribute value
vector before it is changed.
- Version:
- $Revision: 1.3 $
- Author:
- Eibe Frank (eibe@cs.waikato.ac.nz)
-
Instance(double, double[])
- Constructor that inititalizes instance variable with given
values.
-
Instance(Instance)
- Constructor that copies the attribute values and the weight from
the given instance.
-
Instance(int)
- Constructor of an instance that sets weight to one, all values to
be missing, and the reference to the dataset to null.
-
attribute(int)
- Returns the attribute with the given index.
-
classAttribute()
- Returns class attribute.
-
classIndex()
- Returns the class attribute's index.
-
classIsMissing()
- Tests if an instance's class is missing.
-
classValue()
- Returns an instance's class value in internal format.
-
copy()
- Produces a shallow copy of this instance.
-
dataset()
- Returns the dataset this instance has access to.
-
deleteAttributeAt(int)
- Deletes an attribute at the given position (0 to
numAttributes() - 1).
-
enumerateAttributes()
- Returns an enumeration of all the attributes.
-
equalHeaders(Instance)
- Tests if the headers of two instances are equivalent.
-
insertAttributeAt(int)
- Inserts an attribute at the given position (0 to
numAttributes()).
-
isMissing(Attribute)
- Tests if a specific value is "missing".
-
isMissing(int)
- Tests if a specific value is "missing".
-
isMissingValue(double)
- Tests if the given value codes "missing".
-
main(String[])
- Main method for testing this class.
-
missingValue()
- Returns the double that codes "missing".
-
numAttributes()
- Returns the number of attributes.
-
numClasses()
- Returns the number of class labels.
-
replaceMissingValues(double[])
-
Replaces all missing values in the instance with the modes
and means contained in the given array.
-
setClassMissing()
- Sets the class value of an instance to be "missing".
-
setClassValue(double)
- Sets the class value of an instance to the given value (internal
floating-point format).
-
setClassValue(String)
- Sets the class value of an instance to the given value.
-
setDataset(Instances)
- Sets the reference to the dataset.
-
setMissing(Attribute)
- Sets a specific value to be "missing".
-
setMissing(int)
- Sets a specific value to be "missing".
-
setValue(Attribute, double)
- Sets a specific value in the instance to the given value
(internal floating-point format).
-
setValue(Attribute, String)
- Sets a value of an nominal or string attribute to the given
value.
-
setValue(int, double)
- Sets a specific value in the instance to the given value
(internal floating-point format).
-
setValue(int, String)
- Sets a value of a nominal or string attribute to the given
value.
-
setWeight(double)
- Sets the weight of an instance.
-
stringValue(Attribute)
-
Returns the value of a nominal (or string) attribute
for the instance.
-
stringValue(int)
-
Returns the value of a nominal (or string) attribute
for the instance.
-
toString()
- Returns the description of one instance.
-
toString(Attribute)
- Returns the description of one value of the instance as a
string.
-
toString(int)
- Returns the description of one value of the instance as a
string.
-
value(Attribute)
- Returns an instance's attribute value in internal format.
-
value(int)
- Returns an instance's attribute value in internal format.
-
weight()
- Returns the instance's weight.
Instance
public Instance(Instance instance)
- Constructor that copies the attribute values and the weight from
the given instance. Reference to the dataset is set to null.
(ie. the instance doesn't have access to information about the
attribute types)
- Parameters:
- instance - the instance from which the attribute
values and the weight are to be copied
Instance
public Instance(double weight,
double attValues[])
- Constructor that inititalizes instance variable with given
values. Reference to the dataset is set to null. (ie. the instance
doesn't have access to information about the attribute types)
- Parameters:
- weight - the instance's weight
- attValues - a vector of attribute values
Instance
public Instance(int numAttributes)
- Constructor of an instance that sets weight to one, all values to
be missing, and the reference to the dataset to null. (ie. the instance
doesn't have access to information about the attribute types)
- Parameters:
- numAttributes - the size of the instance
attribute
public final Attribute attribute(int index) throws Exception
- Returns the attribute with the given index.
- Parameters:
- index - the attribute's index
- Returns:
- the attribute at the given position
- Throws: Exception
- if instance doesn't have access to a
dataset
classAttribute
public final Attribute classAttribute() throws Exception
- Returns class attribute.
- Returns:
- the class attribute
- Throws: Exception
- if the class is not set or the
instance doesn't have access to a dataset
classIndex
public final int classIndex() throws Exception
- Returns the class attribute's index.
- Returns:
- the class index as an integer
- Throws: Exception
- if instance doesn't have access to a dataset
classIsMissing
public final boolean classIsMissing() throws Exception
- Tests if an instance's class is missing.
- Returns:
- true if the instance's class is missing
- Throws: Exception
- if the class is not set or the instance doesn't
have access to a dataset
classValue
public final double classValue() throws Exception
- Returns an instance's class value in internal format. (ie. as a
floating-point number)
- Returns:
- the corresponding value as a double (If the
corresponding attribute is nominal (or a string) then it returns the
value's index as a double).
- Throws: Exception
- if the class is not set or the instance doesn't
have access to a dataset
copy
public final Object copy()
- Produces a shallow copy of this instance. The copy doesn't have
access to a dataset.
- Returns:
- the shallow copy
dataset
public final Instances dataset()
- Returns the dataset this instance has access to. (ie. obtains
information about attribute types from) Null if the instance
doesn't have access to a dataset.
- Returns:
- the dataset the instance has accesss to
deleteAttributeAt
public final void deleteAttributeAt(int position) throws Exception
- Deletes an attribute at the given position (0 to
numAttributes() - 1). Only succeeds if the instance does not
have access to any dataset because otherwise inconsistencies
could be introduced.
- Parameters:
- pos - the attribute's position
- Throws: Exception
- if the instance has access to a
dataset
enumerateAttributes
public Enumeration enumerateAttributes() throws Exception
- Returns an enumeration of all the attributes.
- Returns:
- enumeration of all the attributes
- Throws: Exception
- if the instance doesn't
have access to a dataset
equalHeaders
public final boolean equalHeaders(Instance inst) throws Exception
- Tests if the headers of two instances are equivalent.
- Parameters:
- instance - another instance
- Returns:
- true if the header of the given instance is
equivalent to this instance's header
- Throws: Exception
- if instance doesn't have access to any
dataset
insertAttributeAt
public final void insertAttributeAt(int position) throws Exception
- Inserts an attribute at the given position (0 to
numAttributes()). Only succeeds if the instance does not
have access to any dataset because otherwise inconsistencies
could be introduced.
- Parameters:
- pos - the attribute's position
- Throws: Exception
- if the instance has accesss to a
dataset, or the position is out of range
isMissing
public final boolean isMissing(int attIndex)
- Tests if a specific value is "missing".
- Parameters:
- attIndex - the attribute's index
isMissing
public final boolean isMissing(Attribute att)
- Tests if a specific value is "missing".
The given attribute has to belong to a dataset.
- Parameters:
- att - the attribute
isMissingValue
public static boolean isMissingValue(double val)
- Tests if the given value codes "missing".
- Parameters:
- val - the value to be tested
- Returns:
- true if val codes "missing"
missingValue
public static double missingValue()
- Returns the double that codes "missing".
- Returns:
- the double that codes "missing"
numAttributes
public final int numAttributes()
- Returns the number of attributes.
- Returns:
- the number of attributes as an integer
numClasses
public final int numClasses() throws Exception
- Returns the number of class labels.
- Returns:
- the number of class labels as an integer if the
class attribute is nominal, 1 otherwise.
- Throws: Exception
- if instance doesn't have access to any
dataset
replaceMissingValues
public final void replaceMissingValues(double array[]) throws Exception
- Replaces all missing values in the instance with the modes
and means contained in the given array. A deep copy of
the vector of attribute values is performed before the
values are replaced.
- Parameters:
- array - containing the means and modes
- Throws: Exception
- if numbers of attributes are unequal
setClassMissing
public final void setClassMissing() throws Exception
- Sets the class value of an instance to be "missing". A deep copy of
the vector of attribute values is performed before the
value is set to be missing.
- Throws: Exception
- if the class is not set or the instance doesn't
have access to a dataset
setClassValue
public final void setClassValue(double value) throws Exception
- Sets the class value of an instance to the given value (internal
floating-point format). A deep copy of the vector of attribute
values is performed before the value is set.
- Parameters:
- value - the new attribute value (If the corresponding
attribute is nominal (or a string) then this is the new value's
index as a double).
- Throws: Exception
- if the class is not set or the instance doesn't
have access to a dataset
setClassValue
public final void setClassValue(String value) throws Exception
- Sets the class value of an instance to the given value. A deep
copy of the vector of attribute values is performed before the
value is set.
- Parameters:
- value - the new class value (If the class
is a string attribute and the value can't be found,
the value is added to the attribute).
- Throws: Exception
- if the dataset or the class is not set, or the
attribute is not nominal or a string, or the value couldn't
be found for a nominal attribute
setDataset
public final void setDataset(Instances instances)
- Sets the reference to the dataset. Does not check if the instance
is compatible with the dataset. Note: the dataset does not know
about this instance. If the structure of the dataset's header
gets changed, this instance will not be adjusted automatically.
- Parameters:
- instances - the reference to the dataset
setMissing
public final void setMissing(int attIndex)
- Sets a specific value to be "missing". Performs a deep copy
of the vector of attribute values before the value is set to
be missing.
- Parameters:
- attIndex - the attribute's index
setMissing
public final void setMissing(Attribute att)
- Sets a specific value to be "missing". Performs a deep copy
of the vector of attribute values before the value is set to
be missing. The given attribute has to belong to a dataset.
- Parameters:
- att - the attribute
setValue
public final void setValue(int attIndex,
double value)
- Sets a specific value in the instance to the given value
(internal floating-point format). Performs a deep copy
of the vector of attribute values before the value is set.
- Parameters:
- attIndex - the attribute's index
- value - the new attribute value (If the corresponding
attribute is nominal (or a string) then this is the new value's
index as a double).
setValue
public final void setValue(int attIndex,
String value) throws Exception
- Sets a value of a nominal or string attribute to the given
value. Performs a deep copy of the vector of attribute values
before the value is set.
- Parameters:
- attIndex - the attribute's index
- value - the new attribute value (If the attribute
is a string attribute and the value can't be found,
the value is added to the attribute).
- Throws: Exception
- if the dataset is not set, or the
attribute is not nominal or a string, or the value couldn't
be found for a nominal attribute
setValue
public final void setValue(Attribute att,
double value)
- Sets a specific value in the instance to the given value
(internal floating-point format). Performs a deep copy of the
vector of attribute values before the value is set.
The given attribute has to belong to a dataset.
- Parameters:
- att - the attribute
- value - the new attribute value (If the corresponding
attribute is nominal (or a string) then this is the new value's
index as a double).
setValue
public final void setValue(Attribute att,
String value) throws Exception
- Sets a value of an nominal or string attribute to the given
value. Performs a deep copy of the vector of attribute values
before the value is set. The given attribute has to belong to a dataset.
- Parameters:
- att - the attribute
- value - the new attribute value (If the attribute
is a string attribute and the value can't be found,
the value is added to the attribute).
- Throws: Exception
- if the the attribute is not nominal or a
string, or the value couldn't be found for a nominal attribute
setWeight
public final void setWeight(double weight)
- Sets the weight of an instance.
- Parameters:
- weight - the weight
stringValue
public final String stringValue(int attIndex) throws Exception
- Returns the value of a nominal (or string) attribute
for the instance.
- Parameters:
- attIndex - the attribute's index
- Returns:
- the value as a string
- Throws: Exception
- if the attribute is not a nominal
(or string) attribute, or the instance doesn't belong
to a dataset.
stringValue
public final String stringValue(Attribute att) throws Exception
- Returns the value of a nominal (or string) attribute
for the instance.
- Parameters:
- att - the attribute
- Returns:
- the value as a string
- Throws: Exception
- if the attribute is not a nominal
(or string) attribute, or the instance doesn't belong
to a dataset.
toString
public final String toString()
- Returns the description of one instance. If the instance
doesn't have access to a dataset, it returns the internal
floating-point values. Quotes string
values that contain whitespace characters.
- Returns:
- the instance's description as a string
- Overrides:
- toString in class Object
toString
public final String toString(int attIndex)
- Returns the description of one value of the instance as a
string. If the instance doesn't have access to a dataset, it
returns the internal floating-point value. Quotes string
values that contain whitespace characters, or if they
are a question mark.
- Parameters:
- attIndex - the attribute's index
- Returns:
- the value's description as a string
toString
public final String toString(Attribute att)
- Returns the description of one value of the instance as a
string. If the instance doesn't have access to a dataset it
returns the internal floating-point value. Quotes string
values that contain whitespace characters, or if they
are a question mark.
The given attribute has to belong to a dataset.
- Parameters:
- att - the attribute
- Returns:
- the value's description as a string
value
public final double value(int attIndex)
- Returns an instance's attribute value in internal format.
- Parameters:
- attIndex - the attribute's index
- Returns:
- the specified value as a double (If the corresponding
attribute is nominal (or a string) then it returns the value's index as a
double).
value
public final double value(Attribute att)
- Returns an instance's attribute value in internal format.
The given attribute has to belong to a dataset.
- Parameters:
- att - the attribute
- Returns:
- the specified value as a double (If the corresponding
attribute is nominal (or a string) then it returns the value's index as a
double).
weight
public final double weight()
- Returns the instance's weight.
- Returns:
- the instance's weight as a double
main
public static void main(String options[])
- Main method for testing this class.
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