Package stdlib

Class StdStats

java.lang.Object
stdlib.StdStats
public final class StdStats extends Object
This class provides static methods for computing statistics such as min, max, mean, sample standard deviation, and sample variance.

For additional documentation, see Section 2.2 of Computer Science: An Interdisciplinary Approach by Robert Sedgewick and Kevin Wayne.

Author:
Robert Sedgewick, Kevin Wayne

  • Method Summary

    Modifier and Type
    Method
    Description
    static void
    main(String[] args)
    Unit tests StdStats.
    static double
    max(double[] a)
    Returns the maximum value in the specified array.
    static double
    max(double[] a, int lo, int hi)
    Returns the maximum value in the specified subarray.
    static int
    max(int[] a)
    Returns the maximum value in the specified array.
    static double
    mean(double[] a)
    Returns the average value in the specified array.
    static double
    mean(double[] a, int lo, int hi)
    Returns the average value in the specified subarray.
    static double
    mean(int[] a)
    Returns the average value in the specified array.
    static double
    min(double[] a)
    Returns the minimum value in the specified array.
    static double
    min(double[] a, int lo, int hi)
    Returns the minimum value in the specified subarray.
    static int
    min(int[] a)
    Returns the minimum value in the specified array.
    static void
    plotBars(double[] a)
    Plots bars from (0, ai) to (ai) for each i to standard draw.
    static void
    plotLines(double[] a)
    Plots the line segments connecting (i, ai) to (i+1, ai+1) for each i to standard draw.
    static void
    plotPoints(double[] a)
    Plots the points (0, a0), (1, a1), ..., (n-1, an-1) to standard draw.
    static double
    stddev(double[] a)
    Returns the sample standard deviation in the specified array.
    static double
    stddev(double[] a, int lo, int hi)
    Returns the sample standard deviation in the specified subarray.
    static double
    stddev(int[] a)
    Returns the sample standard deviation in the specified array.
    static double
    stddevp(double[] a)
    Returns the population standard deviation in the specified array.
    static double
    stddevp(double[] a, int lo, int hi)
    Returns the population standard deviation in the specified subarray.
    static double
    var(double[] a)
    Returns the sample variance in the specified array.
    static double
    var(double[] a, int lo, int hi)
    Returns the sample variance in the specified subarray.
    static double
    var(int[] a)
    Returns the sample variance in the specified array.
    static double
    varp(double[] a)
    Returns the population variance in the specified array.
    static double
    varp(double[] a, int lo, int hi)
    Returns the population variance in the specified subarray.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Method Details

    • max

      public static double max(double[] a)
      Returns the maximum value in the specified array.
      Parameters:
      a - the array
      Returns:
      the maximum value in the array a[]; Double.NEGATIVE_INFINITY if no such value

    • max

      public static double max(double[] a, int lo, int hi)
      Returns the maximum value in the specified subarray.
      Parameters:
      a - the array
      lo - the left endpoint of the subarray (inclusive)
      hi - the right endpoint of the subarray (exclusive)
      Returns:
      the maximum value in the subarray a[lo..hi); Double.NEGATIVE_INFINITY if no such value
      Throws:
      IllegalArgumentException - if a is null
      IllegalArgumentException - unless (0 <= lo) && (lo < hi) && (hi <= a.length)

    • max

      public static int max(int[] a)
      Returns the maximum value in the specified array.
      Parameters:
      a - the array
      Returns:
      the maximum value in the array a[]; Integer.MIN_VALUE if no such value

    • min

      public static double min(double[] a)
      Returns the minimum value in the specified array.
      Parameters:
      a - the array
      Returns:
      the minimum value in the array a[]; Double.POSITIVE_INFINITY if no such value

    • min

      public static double min(double[] a, int lo, int hi)
      Returns the minimum value in the specified subarray.
      Parameters:
      a - the array
      lo - the left endpoint of the subarray (inclusive)
      hi - the right endpoint of the subarray (exclusive)
      Returns:
      the maximum value in the subarray a[lo..hi); Double.POSITIVE_INFINITY if no such value
      Throws:
      IllegalArgumentException - if a is null
      IllegalArgumentException - unless (0 <= lo) && (lo < hi) && (hi <= a.length)

    • min

      public static int min(int[] a)
      Returns the minimum value in the specified array.
      Parameters:
      a - the array
      Returns:
      the minimum value in the array a[]; Integer.MAX_VALUE if no such value

    • mean

      public static double mean(double[] a)
      Returns the average value in the specified array.
      Parameters:
      a - the array
      Returns:
      the average value in the array a[]; Double.NaN if no such value

    • mean

      public static double mean(double[] a, int lo, int hi)
      Returns the average value in the specified subarray.
      Parameters:
      a - the array
      lo - the left endpoint of the subarray (inclusive)
      hi - the right endpoint of the subarray (exclusive)
      Returns:
      the average value in the subarray a[lo..hi); Double.NaN if no such value
      Throws:
      IllegalArgumentException - if a is null
      IllegalArgumentException - unless (0 <= lo) && (lo < hi) && (hi <= a.length)

    • mean

      public static double mean(int[] a)
      Returns the average value in the specified array.
      Parameters:
      a - the array
      Returns:
      the average value in the array a[]; Double.NaN if no such value

    • var

      public static double var(double[] a)
      Returns the sample variance in the specified array.
      Parameters:
      a - the array
      Returns:
      the sample variance in the array a[]; Double.NaN if no such value

    • var

      public static double var(double[] a, int lo, int hi)
      Returns the sample variance in the specified subarray.
      Parameters:
      a - the array
      lo - the left endpoint of the subarray (inclusive)
      hi - the right endpoint of the subarray (exclusive)
      Returns:
      the sample variance in the subarray a[lo..hi); Double.NaN if no such value
      Throws:
      IllegalArgumentException - if a is null
      IllegalArgumentException - unless (0 <= lo) && (lo < hi) && (hi <= a.length)

    • var

      public static double var(int[] a)
      Returns the sample variance in the specified array.
      Parameters:
      a - the array
      Returns:
      the sample variance in the array a[]; Double.NaN if no such value

    • varp

      public static double varp(double[] a)
      Returns the population variance in the specified array.
      Parameters:
      a - the array
      Returns:
      the population variance in the array a[]; Double.NaN if no such value

    • varp

      public static double varp(double[] a, int lo, int hi)
      Returns the population variance in the specified subarray.
      Parameters:
      a - the array
      lo - the left endpoint of the subarray (inclusive)
      hi - the right endpoint of the subarray (exclusive)
      Returns:
      the population variance in the subarray a[lo..hi); Double.NaN if no such value
      Throws:
      IllegalArgumentException - if a is null
      IllegalArgumentException - unless (0 <= lo) && (lo < hi) && (hi <= a.length)

    • stddev

      public static double stddev(double[] a)
      Returns the sample standard deviation in the specified array.
      Parameters:
      a - the array
      Returns:
      the sample standard deviation in the array a[]; Double.NaN if no such value

    • stddev

      public static double stddev(int[] a)
      Returns the sample standard deviation in the specified array.
      Parameters:
      a - the array
      Returns:
      the sample standard deviation in the array a[]; Double.NaN if no such value

    • stddev

      public static double stddev(double[] a, int lo, int hi)
      Returns the sample standard deviation in the specified subarray.
      Parameters:
      a - the array
      lo - the left endpoint of the subarray (inclusive)
      hi - the right endpoint of the subarray (exclusive)
      Returns:
      the sample standard deviation in the subarray a[lo..hi); Double.NaN if no such value
      Throws:
      IllegalArgumentException - if a is null
      IllegalArgumentException - unless (0 <= lo) && (lo < hi) && (hi <= a.length)

    • stddevp

      public static double stddevp(double[] a)
      Returns the population standard deviation in the specified array.
      Parameters:
      a - the array
      Returns:
      the population standard deviation in the array; Double.NaN if no such value

    • stddevp

      public static double stddevp(double[] a, int lo, int hi)
      Returns the population standard deviation in the specified subarray.
      Parameters:
      a - the array
      lo - the left endpoint of the subarray (inclusive)
      hi - the right endpoint of the subarray (exclusive)
      Returns:
      the population standard deviation in the subarray a[lo..hi); Double.NaN if no such value
      Throws:
      IllegalArgumentException - if a is null
      IllegalArgumentException - unless (0 <= lo) && (lo < hi) && (hi <= a.length)

    • plotPoints

      public static void plotPoints(double[] a)
      Plots the points (0, a0), (1, a1), ..., (n-1, an-1) to standard draw.
      Parameters:
      a - the array of values

    • plotLines

      public static void plotLines(double[] a)
      Plots the line segments connecting (i, ai) to (i+1, ai+1) for each i to standard draw.
      Parameters:
      a - the array of values

    • plotBars

      public static void plotBars(double[] a)
      Plots bars from (0, ai) to (ai) for each i to standard draw.
      Parameters:
      a - the array of values

    • main

      public static void main(String[] args)
      Unit tests StdStats. Convert command-line arguments to array of doubles and call various methods.
      Parameters:
      args - the command-line arguments