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Statistical Variables
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User's Guide
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A variable is a collection of observations of a characteristic
of an object that can take on two or more values. This chapter
provides an overview of how variables are implemented in the
Extreme Optimizaton Numerical Libraries for .NET.
Variables occur in two situations, either on their own or as
part of a collection. On their own, you can use them to calculate
descriptive statistics, like the mean and the standard deviation.
Or you can use it to perform statistical tests, such as the
one-sample z test or Kolmogorov-Smirnov goodness-of-fit
test. Most often, however, variables will come in groups and
represent different properties or measurements in a data set.
In the Extreme Optimization Numerical Libraries for
.NET, variables are implemented by the Variable class. This
is an abstract base class that provides the base functionality for
all variable types.
Variables can be either continuous, or categorical.
Continuous Variables
Any variable that can take on a value from a continuous range is
called a continuous variable. The Extreme Optimization
Numerical Libraries for .NET supports two kinds of continuous
variables. Numerical variables, implemented by
the NumericalVariable class, can represent
any numerical value. Time variables, implemented by
the DateTimeVariable class,
can represent instances in time.
Categorical Variables
Variables whose observations can take on only one of a finite
set of values are called categorical variables or discrete
variables, and are implemented by the CategoricalVariable class.
Fundamental to the implementation of categorical variables is
the concept of a scale. A scale represents the possible values that
a variable can have. Every categorical variable has an
associated scale. The scale is used to map an object to its
category, or to the index of its category in a list of
categories.
Variable Collections
Most statistical data sets are made up of several variables.
This functionality is encapsulated in a VariableCollection
object. Variable collections can be created by adding
individual variables, and by importing them from ADO.NET objects
like data tables and data readers.
The next three chapters cover the above three topics in greater
detail.
Up: Statistics Library Next: Continuous Variables Previous: Statistics Library Contents
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