package stdlib;

/* ***********************************************************************
 *  Compilation:  javac StdStats.java
 *  Execution:    java StdStats < input.txt
 *
 *  Library of statistical functions.
 *
 *  The test client reads an array of real numbers from standard
 *  input, and computes the minimum, mean, maximum, and
 *  standard deviation.
 *
 *  The functions all throw a NullPointerException if the array
 *  passed in is null.

 *  % more tiny.txt
 *  5
 *  3.0 1.0 2.0 5.0 4.0
 *
 *  % java StdStats < tiny.txt
 *         min   1.000
 *        mean   3.000
 *         max   5.000
 *     std dev   1.581
 *
 *************************************************************************/

/**
 *  <i>Standard statistics</i>. This class provides methods for computing
 *  statistics such as min, max, mean, sample standard deviation, and
 *  sample variance.
 *  <p>
 *  For additional documentation, see
 *  <a href="http://introcs.cs.princeton.edu/22library">Section 2.2</a> of
 *  <i>Introduction to Programming in Java: An Interdisciplinary Approach</i>
 *  by Robert Sedgewick and Kevin Wayne.
 */
public final class StdStats {

  private StdStats() { }

  /**
   * Return maximum value in array, -infinity if no such value.
   */
  public static double max(double[] a) {
    double max = Double.NEGATIVE_INFINITY;
    for (int i = 0; i < a.length; i++) {
      if (a[i] > max) max = a[i];
    }
    return max;
  }

  /**
   * Return maximum value in subarray a[lo..hi], -infinity if no such value.
   */
  public static double max(double[] a, int lo, int hi) {
    if (lo < 0 || hi >= a.length || lo > hi)
      throw new RuntimeException("Subarray indices out of bounds");
    double max = Double.NEGATIVE_INFINITY;
    for (int i = lo; i <= hi; i++) {
      if (a[i] > max) max = a[i];
    }
    return max;
  }

  /**
   * Return maximum value of array, Integer.MIN_VALUE if no such value
   */
  public static int max(int[] a) {
    int max = Integer.MIN_VALUE;
    for (int i = 0; i < a.length; i++) {
      if (a[i] > max) max = a[i];
    }
    return max;
  }

  /**
   * Return minimum value in array, +infinity if no such value.
   */
  public static double min(double[] a) {
    double min = Double.POSITIVE_INFINITY;
    for (int i = 0; i < a.length; i++) {
      if (a[i] < min) min = a[i];
    }
    return min;
  }

  /**
   * Return minimum value in subarray a[lo..hi], +infinity if no such value.
   */
  public static double min(double[] a, int lo, int hi) {
    if (lo < 0 || hi >= a.length || lo > hi)
      throw new RuntimeException("Subarray indices out of bounds");
    double min = Double.POSITIVE_INFINITY;
    for (int i = lo; i <= hi; i++) {
      if (a[i] < min) min = a[i];
    }
    return min;
  }

  /**
   * Return minimum value of array, Integer.MAX_VALUE if no such value
   */
  public static int min(int[] a) {
    int min = Integer.MAX_VALUE;
    for (int i = 0; i < a.length; i++) {
      if (a[i] < min) min = a[i];
    }
    return min;
  }

  /**
   * Return average value in array, NaN if no such value.
   */
  public static double mean(double[] a) {
    if (a.length == 0) return Double.NaN;
    double sum = sum(a);
    return sum / a.length;
  }

  /**
   * Return average value in subarray a[lo..hi], NaN if no such value.
   */
  public static double mean(double[] a, int lo, int hi) {
    int length = hi - lo + 1;
    if (lo < 0 || hi >= a.length || lo > hi)
      throw new RuntimeException("Subarray indices out of bounds");
    if (length == 0) return Double.NaN;
    double sum = sum(a, lo, hi);
    return sum / length;
  }

  /**
   * Return average value in array, NaN if no such value.
   */
  public static double mean(int[] a) {
    if (a.length == 0) return Double.NaN;
    double sum = 0.0;
    for (int i = 0; i < a.length; i++) {
      sum = sum + a[i];
    }
    return sum / a.length;
  }

  /**
   * Return sample variance of array, NaN if no such value.
   */
  public static double var(double[] a) {
    if (a.length == 0) return Double.NaN;
    double avg = mean(a);
    double sum = 0.0;
    for (int i = 0; i < a.length; i++) {
      sum += (a[i] - avg) * (a[i] - avg);
    }
    return sum / (a.length - 1);
  }

  /**
   * Return sample variance of subarray a[lo..hi], NaN if no such value.
   */
  public static double var(double[] a, int lo, int hi) {
    int length = hi - lo + 1;
    if (lo < 0 || hi >= a.length || lo > hi)
      throw new RuntimeException("Subarray indices out of bounds");
    if (length == 0) return Double.NaN;
    double avg = mean(a, lo, hi);
    double sum = 0.0;
    for (int i = lo; i <= hi; i++) {
      sum += (a[i] - avg) * (a[i] - avg);
    }
    return sum / (length - 1);
  }

  /**
   * Return sample variance of array, NaN if no such value.
   */
  public static double var(int[] a) {
    if (a.length == 0) return Double.NaN;
    double avg = mean(a);
    double sum = 0.0;
    for (int i = 0; i < a.length; i++) {
      sum += (a[i] - avg) * (a[i] - avg);
    }
    return sum / (a.length - 1);
  }

  /**
   * Return population variance of array, NaN if no such value.
   */
  public static double varp(double[] a) {
    if (a.length == 0) return Double.NaN;
    double avg = mean(a);
    double sum = 0.0;
    for (int i = 0; i < a.length; i++) {
      sum += (a[i] - avg) * (a[i] - avg);
    }
    return sum / a.length;
  }

  /**
   * Return population variance of subarray a[lo..hi],  NaN if no such value.
   */
  public static double varp(double[] a, int lo, int hi) {
    int length = hi - lo + 1;
    if (lo < 0 || hi >= a.length || lo > hi)
      throw new RuntimeException("Subarray indices out of bounds");
    if (length == 0) return Double.NaN;
    double avg = mean(a, lo, hi);
    double sum = 0.0;
    for (int i = lo; i <= hi; i++) {
      sum += (a[i] - avg) * (a[i] - avg);
    }
    return sum / length;
  }


  /**
   * Return sample standard deviation of array, NaN if no such value.
   */
  public static double stddev(double[] a) {
    return Math.sqrt(var(a));
  }

  /**
   * Return sample standard deviation of subarray a[lo..hi], NaN if no such value.
   */
  public static double stddev(double[] a, int lo, int hi) {
    return Math.sqrt(var(a, lo, hi));
  }

  /**
   * Return sample standard deviation of array, NaN if no such value.
   */
  public static double stddev(int[] a) {
    return Math.sqrt(var(a));
  }

  /**
   * Return population standard deviation of array, NaN if no such value.
   */
  public static double stddevp(double[] a) {
    return Math.sqrt(varp(a));
  }

  /**
   * Return population standard deviation of subarray a[lo..hi], NaN if no such value.
   */
  public static double stddevp(double[] a, int lo, int hi) {
    return Math.sqrt(varp(a, lo, hi));
  }

  /**
   * Return sum of all values in array.
   */
  public static double sum(double[] a) {
    double sum = 0.0;
    for (int i = 0; i < a.length; i++) {
      sum += a[i];
    }
    return sum;
  }

  /**
   * Return sum of all values in subarray a[lo..hi].
   */
  public static double sum(double[] a, int lo, int hi) {
    if (lo < 0 || hi >= a.length || lo > hi)
      throw new RuntimeException("Subarray indices out of bounds");
    double sum = 0.0;
    for (int i = lo; i <= hi; i++) {
      sum += a[i];
    }
    return sum;
  }

  /**
   * Return sum of all values in array.
   */
  public static int sum(int[] a) {
    int sum = 0;
    for (int i = 0; i < a.length; i++) {
      sum += a[i];
    }
    return sum;
  }

  /**
   * Plot points (i, a[i]) to standard draw.
   */
  public static void plotPoints(double[] a) {
    int N = a.length;
    StdDraw.setXscale(0, N-1);
    StdDraw.setPenRadius(1.0 / (3.0 * N));
    for (int i = 0; i < N; i++) {
      StdDraw.point(i, a[i]);
    }
  }

  /**
   * Plot line segments connecting points (i, a[i]) to standard draw.
   */
  public static void plotLines(double[] a) {
    int N = a.length;
    StdDraw.setXscale(0, N-1);
    StdDraw.setPenRadius();
    for (int i = 1; i < N; i++) {
      StdDraw.line(i-1, a[i-1], i, a[i]);
    }
  }

  /**
   * Plot bars from (0, a[i]) to (i, a[i]) to standard draw.
   */
  public static void plotBars(double[] a) {
    int N = a.length;
    StdDraw.setXscale(0, N-1);
    for (int i = 0; i < N; i++) {
      StdDraw.filledRectangle(i, a[i]/2, .25, a[i]/2);
    }
  }


  /**
   * Test client.
   * Convert command-line arguments to array of doubles and call various methods.
   */
  public static void main(String[] args) {
    double[] a = ArrayGenerator.readDouble1D(new In ());
    StdOut.format("       min %7.3f\n", min(a));
    StdOut.format("      mean %7.3f\n", mean(a));
    StdOut.format("       max %7.3f\n", max(a));
    StdOut.format("   std dev %7.3f\n", stddev(a));
  }
}