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## org.apache.commons.math.random
Interface EmpiricalDistribution

All Known Implementing Classes:
  EmpiricalDistributionImpl

public interface EmpiricalDistribution

Represents an empirical probability distribution -- a probability distribution derived from observed data without making any assumptions about the functional form of the population distribution that the data come from.

Implementations of this interface maintain data structures, called distribution digests, that describe empirical distributions and support the following operations:

- loading the distribution from a file of observed data values
- dividing the input data into "bin ranges" and reporting bin frequency counts (data for histogram)
- reporting univariate statistics describing the full set of data values as well as the observations within each bin
- generating random values from the distribution

Applications can use `EmpiricalDistribution` implementations to build grouped frequnecy histograms representing the input data or to generate random values "like" those in the input file -- i.e., the values generated will follow the distribution of the values in the file.

Version:
  $Revision: 1.23 $ $Date: 2004/10/08 05:08:16 $

Method Summary
`int` | `getBinCount()` Returns the number of bins.
`List` | `getBinStats()` Returns a list of `SummaryStatistics` containing statistics describing the values in each of the bins.
`double` | `getNextValue()` Generates a random value from this distribution.
`StatisticalSummary` | `getSampleStats()` Returns a `StatisticalSummary` describing this distribution.
`double[]` | `getUpperBounds()` Returns the array of upper bounds for the bins.
`boolean` | `isLoaded()` Property indicating whether or not the distribution has been loaded.
`void` | `load(double[] dataArray)` Computes the empirical distribution from the provided array of numbers.
`void` | `load(File file)` Computes the empirical distribution from the input file.
`void` | `load(URL url)` Computes the empirical distribution using data read from a URL.

Method Detail

### load

    public void load(double[] dataArray)

  Computes the empirical distribution from the provided array of numbers.

  Parameters:
    `dataArray` - the data array

### load

    public void load(File file)
              throws IOException

  Computes the empirical distribution from the input file.

  Parameters:
    `file` - the input file
  Throws:
    `IOException` - if an IO error occurs

### load

    public void load(URL url)
              throws IOException

  Computes the empirical distribution using data read from a URL.

  Parameters:
    `url` - url of the input file
  Throws:
    `IOException` - if an IO error occurs

### getNextValue

    public double getNextValue()
                        throws IllegalStateException

  Generates a random value from this distribution. Preconditions:
  - the distribution must be loaded before invoking this method

  Returns:
    the random value.
  Throws:
    `IllegalStateException` - if the distribution has not been loaded

### getSampleStats

    public StatisticalSummary getSampleStats()
                                      throws IllegalStateException

  Returns a `StatisticalSummary` describing this distribution. Preconditions:
  - the distribution must be loaded before invoking this method

  Returns:
    the sample statistics
  Throws:
    `IllegalStateException` - if the distribution has not been loaded

### isLoaded

    public boolean isLoaded()

  Property indicating whether or not the distribution has been loaded.

  Returns:
    true if the distribution has been loaded

### getBinCount

    public int getBinCount()

  Returns the number of bins.

  Returns:
    the number of bins

### getBinStats

    public List getBinStats()

  Returns a list of `SummaryStatistics` containing statistics describing the values in each of the bins. The List is indexed on the bin number.

  Returns:
    List of bin statistics

### getUpperBounds

    public double[] getUpperBounds()

  Returns the array of upper bounds for the bins. Bins are:
  [min,upperBounds[0]],(upperBounds[0],upperBounds[1]],..., (upperBounds[binCount-1],max].

  Returns:
    array of bin upper bounds

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