ibis.util
Class Stats

java.lang.Object
  ibis.util.Stats

public final class Stats

extends java.lang.Object

Class for doing some recurring statistical calculations.

Method Summary

static double	mbs(double bytes, double millis) Calculates a speed in Mb/s given the size in bytes and the time in milliseconds.
static double	mbs(double bytes, double[] millis, int off, int len) Calculates a speed in Mb/s given the size in bytes and a number of times in milliseconds.
static double	mean(double[] data) Calculates the mean of an array of numbers.
static double	mean(double[] data, int off, int len) Calculates the mean of a subset of an array of numbers.
static double	round(double v) Rounds up a double.
static double	stdDev(double[] data) Calculates the standard deviation of an array of numbers.
static double	stdDev(double[] data, int off, int len) Calculates the standard deviation of a subset of an array of numbers.
static double	stdDevError(double[] data, int off, int len) Returns the standard deviation as a percentage of the mean.

Methods inherited from class java.lang.Object

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

Method Detail

mean

public static double mean(double[] data)

Calculates the mean of an array of numbers.

Parameters:

data - the numbers to calculate the mean of.

Returns:

the mean.

mean

public static double mean(double[] data,
                          int off,
                          int len)

Calculates the mean of a subset of an array of numbers.

Parameters:

data - the numbers to calculate the mean of

off - offset

len - length

Returns:

the mean.

stdDev

public static double stdDev(double[] data)

Calculates the standard deviation of an array of numbers. See http://www.davidmlane.com/hyperstat/A16252.html

Parameters:

data - the numbers to calculate the standard deviation of.

Returns:

the standard deviation.

stdDev

public static double stdDev(double[] data,
                            int off,
                            int len)

Calculates the standard deviation of a subset of an array of numbers. See http://www.davidmlane.com/hyperstat/A16252.html

Parameters:

data - the numbers to calculate the standard deviation of

off - offset

len - length

Returns:

the standard deviation.

mbs

public static double mbs(double bytes,
                         double millis)

Calculates a speed in Mb/s given the size in bytes and the time in milliseconds. The result is rounded to one hundreth of an integer

Parameters:

bytes - size of the data in bytes

millis - the time of the measurement in milliseconds

Returns:

the speed.

mbs

public static double mbs(double bytes,
                         double[] millis,
                         int off,
                         int len)

Calculates a speed in Mb/s given the size in bytes and a number of times in milliseconds. The result is rounded to one hundreth of an integer.

Parameters:

bytes - size of the data in bytes

millis - a number of time measurements in milliseconds

off - the first measurement used in the calculation

len - the number of measurements used in the calculation

Returns:

the speed.

round

public static double round(double v)

Rounds up a double. Rounds to one hundreth of an integer.

Parameters:

v - the value to be rounded.

Returns:

the rounded value.

stdDevError

public static double stdDevError(double[] data,
                                 int off,
                                 int len)

Returns the standard deviation as a percentage of the mean. The result is rounded up to a hundredth of an integer.

Parameters:

data - array with input data (numbers)

off - offset in the data at which to start calculating

len - number of array elements to use for the calculation

Returns:

the standard deviation as a percentage.