Data Instance (instance
)¶
Class Instance
represents a data instance, typically retrieved from a
Orange.data.Table
or Orange.data.sql.SqlTable
. The base class
contains a copy of the data; modifying does not change the data in the storage
from which the instance was retrieved. Derived classes
(e.g. Orange.data.table.RowInstance
) can represent views into various
data storages, therefore changing them actually changes the data.
Like data tables, every data instance is associated with a domain and its data is split into attributes, classes, meta attributes and the weight. Its constructor thus requires a domain and, optionally, data. For the following example, we borrow the domain from the Iris dataset.
>>> from Orange.data import Table, Instance
>>> iris = Table("iris")
>>> inst = Instance(iris.domain, [5.2, 3.8, 1.4, 0.5, "Iris-virginica"])
>>> inst
[5.2, 3.8, 1.4, 0.5 | Iris-virginica]
>>> inst0 = Instance(iris.domain)
>>> inst0
[?, ?, ?, ? | ?]
The instance's data can be retrieved through attributes x
, y
and
metas
.
>>> inst.x
array([ 5.2, 3.8, 1.4, 0.5])
>>> inst.y
array([ 2.])
>>> inst.metas
array([], dtype=object)
Other utility functions provide for easier access to the instances data.
>>> inst.get_class()
Value('iris', Iris-virginica)
>>> for e in inst.attributes():
... print(e)
...
5.2
3.8
1.4
0.5
- class Orange.data.Instance(domain, data=None, id=None)[source]¶
Constructor requires a domain and the data as numpy array, an existing instance from the same or another domain or any Python iterable.
Domain can be omitted it the data is given as an existing data instances.
When the instance is not from the given domain, Orange converts it.
>>> from Orange.preprocess import DomainDiscretizer >>> discretizer = DomainDiscretizer() >>> d_iris = discretizer(iris) >>> d_inst = Instance(d_iris, inst)
- property domain¶
The domain describing the instance's values.
- property x¶
Instance's attributes as a 1-dimensional numpy array whose length equals len(self.domain.attributes).
- property y¶
Instance's classes as a 1-dimensional numpy array whose length equals len(self.domain.attributes).
- property metas¶
Instance's meta attributes as a 1-dimensional numpy array whose length equals len(self.domain.attributes).
- property list¶
All instance's values, including attributes, classes and meta attributes, as a list whose length equals len(self.domain.attributes) + len(self.domain.class_vars) + len(self.domain.metas).
- property weight¶
The weight of the data instance. Default is 1.
Rows of Data Tables¶
- class Orange.data.RowInstance(table, row_index)[source]¶
RowInstance is a specialization of
Instance
that represents a row ofOrange.data.Table
. RowInstance is returned by indexing a Table.The difference between Instance and RowInstance is that the latter represents a view into the table: changing the RowInstance changes the data in the table:
>>> iris[42] [4.4, 3.2, 1.3, 0.2 | Iris-setosa] >>> inst = iris[42] >>> inst.set_class("Iris-virginica") >>> iris[42] [4.4, 3.2, 1.3, 0.2 | Iris-virginica]
Dense tables can also be modified directly through
x
,y
andmetas
.>>> inst.x[0] = 5 >>> iris[42] [5.0, 3.2, 1.3, 0.2 | Iris-virginica]
Sparse tables cannot be changed in this way.
- property weight¶
The weight of the data instance. Default is 1.