ilStatistics Class Reference

This class provides mathematical functions for statistics. More...

Collaboration diagram for ilStatistics:

Public Member Functions
	__construct ($nan_handling=NAN_HANDLING_REMOVE)
	Constructor of ilStatistics class. More...
	setNANHandling ($nan_handling=NAN_HANDLING_REMOVE)
	Set the handling of elements which are not a number. More...
	getNANHandling ()
	Get the handling of elements which are not a number. More...
	setData ($stat_data)
	Sets the data and checks for invalid values. More...
	getData ()
	Returns the numeric value array containing the data. More...
	min ()
	Calculates the minimum value. More...
	max ()
	Calculates the maximum value. More...
	count ()
	Calculates number of data values. More...
	sum_n ($n)
	Calculates the sum of x_1^n + x_2^n + ... + x_i^n. More...
	sum ()
	Calculates the sum of x_1 + x_2 + ... + x_i. More...
	sum2 ()
	Calculates the sum of x_1^2 + x_2^2 + ... + x_i^2. More...
	product_n ($n)
	Calculates the product of x_1^n * x_2^n * ... * x_i^n. More...
	product ($n)
	Calculates the product of x_1 * x_2 * ... * x_i. More...
	arithmetic_mean ()
	Arithmetic mean of the data values xbar = (1/n)*∑x_i. More...
	geometric_mean ()
	Geometric mean of the data values geometric_mean = (x_1 * x_2 * ... * x_n)^(1/n) More...
	harmonic_mean ()
	Harmonic mean of the data values harmonic_mean = n/(1/x_1 + 1/x_2 + ... + 1/x_n) More...
	median ()
	Median of the data values. More...
	rank ($value)
	Returns the rank of a given value. More...
	rank_median ()
	Returns the rank of the median. More...
	quantile ($n)
	n-Quantile of the data values More...
	validate ()
	Validates the numeric data and handles values which are not a number according to the $nan_handling variable. More...

Data Fields
	$nan_handling
	$stat_data

Detailed Description

This class provides mathematical functions for statistics.

It works on an array of numeric values.

Author

Helmut Schottmüller hscho.nosp@m.ttm@.nosp@m.tzi.d.nosp@m.e

Version

$Id$

Definition at line 32 of file class.ilStatistics.php.

Constructor & Destructor Documentation

__construct()

ilStatistics::__construct

(

$nan_handling = NAN_HANDLING_REMOVE

)

Constructor of ilStatistics class.

@access public

Definition at line 57 of file class.ilStatistics.php.

    {
        $this->nan_handling = $nan_handling;
        $this->stat_data = array();
    }

References $nan_handling.

Member Function Documentation

arithmetic_mean()

ilStatistics::arithmetic_mean

(

)

Arithmetic mean of the data values xbar = (1/n)*∑x_i.

Returns

mixed The arithmetic mean or false, if there is an error or no values @access public

Definition at line 242 of file class.ilStatistics.php.

    {
        $sum = $this->sum();
        if ($sum === false) {
            return false;
        }
        $count = $this->count();
        if ($count == 0) {
            return false;
        }
        return (float) ($sum / $count);
    }

References count(), and sum().

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count()

ilStatistics::count

(

)

Calculates number of data values.

Returns

mixed The number of data values @access public

Definition at line 154 of file class.ilStatistics.php.

    {
        return count($this->stat_data);
    }

References count().

Referenced by arithmetic_mean(), count(), geometric_mean(), harmonic_mean(), max(), median(), min(), product_n(), quantile(), rank(), rank_median(), and sum_n().

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geometric_mean()

ilStatistics::geometric_mean

(

)

Geometric mean of the data values geometric_mean = (x_1 * x_2 * ... * x_n)^(1/n)

The geometric mean of a set of positive data is defined as the product of all the members of the set, raised to a power equal to the reciprocal of the number of members.

Returns

mixed The geometric mean or false, if there is an error or no values @access public

Definition at line 266 of file class.ilStatistics.php.

    {
        $prod = $this->product(1);
        if (($prod === false) or ($prod === 0)) {
            return false;
        }
        $count = $this->count();
        if ($count == 0) {
            return false;
        }
        return pow((float) $prod, (float) (1 / $count));
    }

References count(), and product().

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getData()

ilStatistics::getData

(

)

Returns the numeric value array containing the data.

Returns

array An array containing the sorted numeric data @access public

Definition at line 109 of file class.ilStatistics.php.

                             : array
    {
        return $this->stat_data;
    }

References $stat_data.

getNANHandling()

ilStatistics::getNANHandling

(

)

Get the handling of elements which are not a number.

Returns NAN_HANDLING_REMOVE if all elements which are not a number will be removed. Returns NAN_HANDLING_ZERO if all elements which are not a number will be set to zero.

Returns

integer A constant defining the handling of elements which are not a number @access public

Definition at line 86 of file class.ilStatistics.php.

                                    : int
    {
        return $this->nan_handling;
    }

References $nan_handling.

harmonic_mean()

ilStatistics::harmonic_mean

(

)

Harmonic mean of the data values harmonic_mean = n/(1/x_1 + 1/x_2 + ... + 1/x_n)

Returns

mixed The harmonic mean or false, if there is an error or no values @access public

Definition at line 286 of file class.ilStatistics.php.

    {
        $min = $this->min();
        if (($min === false) or ($min === 0)) {
            return false;
        }
        $count = $this->count();
        if ($count == 0) {
            return false;
        }
        $sum = 0;
        foreach ($this->stat_data as $value) {
            $sum += 1 / $value;
        }
        return $count / $sum;
    }

References count(), and min().

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max()

ilStatistics::max

(

)

Calculates the maximum value.

Returns

mixed The maximum value or false, if no maximum exists

See also

min() @access public

Definition at line 138 of file class.ilStatistics.php.

    {
        if (count($this->stat_data)) {
            $max = max($this->stat_data);
        } else {
            $max = false;
        }
        return $max;
    }

References count(), and max().

Referenced by max().

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median()

ilStatistics::median

(

)

Median of the data values.

Returns

mixed The median or false, if there are no data values @access public

Definition at line 309 of file class.ilStatistics.php.

    {
        $median = false;
        if (count($this->stat_data)) {
            $median = 0;
            $count = $this->count();
            if ((count($this->stat_data) % 2) == 0) {
                $median = ($this->stat_data[($count / 2) - 1] + $this->stat_data[($count / 2)]) / 2;
            } else {
                $median = $this->stat_data[(($count + 1) / 2) - 1];
            }
        }
        return $median;
    }

References count().

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min()

ilStatistics::min

(

)

Calculates the minimum value.

Returns

mixed The minimum value or false, if no minimum exists

See also

max() @access public

Definition at line 121 of file class.ilStatistics.php.

    {
        if (count($this->stat_data)) {
            $min = min($this->stat_data);
        } else {
            $min = false;
        }
        return $min;
    }

References count(), and min().

Referenced by harmonic_mean(), min(), and product_n().

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product()

ilStatistics::product

(

$n

)

Calculates the product of x_1 * x_2 * ... * x_i.

Parameters

numeric

$n

The exponent

Returns

mixed The product of x_1 * x_2 * ... * x_i or false, if no values exist @access public

Definition at line 230 of file class.ilStatistics.php.

    {
        return $this->product_n(1);
    }

References product_n().

Referenced by geometric_mean().

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product_n()

ilStatistics::product_n

(

$n

)

Calculates the product of x_1^n * x_2^n * ... * x_i^n.

Parameters

numeric

$n

The exponent

Returns

mixed The product of x_1^n * x_2^n * ... * x_i^n or false, if no values exist @access public

Definition at line 208 of file class.ilStatistics.php.

    {
        $prod_n = false;
        if (count($this->stat_data)) {
            if ($this->min() === 0) {
                return 0.0;
            }
            $prod_n = 1.0;
            foreach ($this->stat_data as $value) {
                $prod_n *= pow((float) $value, (float) $n);
            }
        }
        return $prod_n;
    }

References count(), and min().

Referenced by product().

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quantile()

ilStatistics::quantile

(

$n

)

n-Quantile of the data values

Parameters

double

$n

A value between 0 an 100 calculating the n-Quantile

Returns

mixed The n-quantile or false, if there are no data values @access public

Definition at line 374 of file class.ilStatistics.php.

    {
        $count = $this->count();
        if ($count == 0) {
            return false;
        }
        $nprod = ($n / 100) * $count;
        if (intval($nprod) == $nprod) {
            $k = $nprod;
            if ($k == 0) {
                return $this->stat_data[$k];
            } elseif ($k == $count) {
                return $this->stat_data[$k - 1];
            } else {
                return ($this->stat_data[$k - 1] + $this->stat_data[$k]) / 2;
            }
        } else {
            $k = ceil($nprod);
            return $this->stat_data[$k - 1];
        }
    }

References count().

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rank()

ilStatistics::rank

(

$value

)

Returns the rank of a given value.

Returns

mixed The rank, if the value exists in the data, otherwise false @access public

Definition at line 330 of file class.ilStatistics.php.

    {
        if (!is_numeric($value)) {
            return false;
        }
        $rank = array_search($value, $this->stat_data);
        if ($rank !== false) {
            $rank = $this->count() - $rank;
        }
        return $rank;
    }

References count().

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rank_median()

ilStatistics::rank_median

(

)

Returns the rank of the median.

This method is different from the rank method because the median could be the arithmetic mean of the two middle values when the data size is even. In this case the median could a value which is not part of the data set.

Returns

mixed The rank of the median, otherwise false @access public

Definition at line 352 of file class.ilStatistics.php.

    {
        $count = $this->count();
        if ($count == 0) {
            return false;
        }
 
        if (($count % 2) == 0) {
            $rank_median = ($count + 1) / 2;
        } else {
            $rank_median = ($count + 1) / 2;
        }
        return $rank_median;
    }

References count().

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setData()

ilStatistics::setData

(

$stat_data

)

Sets the data and checks for invalid values.

Parameters

array

$stat_data

An array containing the numeric data @access public

Definition at line 97 of file class.ilStatistics.php.

    {
        $this->stat_data = array_values($stat_data);
        $this->validate();
    }

References $stat_data, and validate().

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setNANHandling()

ilStatistics::setNANHandling

(

$nan_handling = NAN_HANDLING_REMOVE

)

Set the handling of elements which are not a number.

If set to NAN_HANDLING_REMOVE, all elements which are not a number will be removed, if set to NAN_HANDLING_ZERO, all elements which are not a number will be set to zero.

Parameters

integer

$nan_handling

A constant defining the handling of elements which are not a number @access public

Definition at line 72 of file class.ilStatistics.php.

    {
        $this->nan_handling = $nan_handling;
    }

References $nan_handling.

sum()

ilStatistics::sum

(

)

Calculates the sum of x_1 + x_2 + ... + x_i.

Returns

mixed The sum of x_1 + x_2 + ... + x_i or false, if no values exist @access public

Definition at line 184 of file class.ilStatistics.php.

    {
        return $this->sum_n(1);
    }

References sum_n().

Referenced by arithmetic_mean().

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sum2()

ilStatistics::sum2

(

)

Calculates the sum of x_1^2 + x_2^2 + ... + x_i^2.

Returns

mixed The sum of x_1^2 + x_2^2 + ... + x_i^2 or false, if no values exist @access public

Definition at line 196 of file class.ilStatistics.php.

    {
        return $this->sum_n(2);
    }

References sum_n().

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sum_n()

ilStatistics::sum_n

(

$n

)

Calculates the sum of x_1^n + x_2^n + ... + x_i^n.

Parameters

numeric

$n

The exponent

Returns

mixed The sum of x_1^n + x_2^n + ... + x_i^n or false, if no values exist @access public

Definition at line 166 of file class.ilStatistics.php.

    {
        $sum_n = false;
        if (count($this->stat_data)) {
            $sum_n = 0;
            foreach ($this->stat_data as $value) {
                $sum_n += pow((float) $value, (float) $n);
            }
        }
        return $sum_n;
    }

References count().

Referenced by sum(), and sum2().

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validate()

ilStatistics::validate

(

)

Validates the numeric data and handles values which are not a number according to the $nan_handling variable.

After validation the data is sorted.

Returns

boolean Returns true on success, otherwise false @access private

Definition at line 404 of file class.ilStatistics.php.

                              : bool
    {
        $result = true;
        foreach ($this->stat_data as $key => $value) {
            if (!is_numeric($value)) {
                switch ($this->nan_handling) {
                    case NAN_HANDLING_REMOVE:
                        unset($this->stat_data[$key]);
                        break;
                    case NAN_HANDLING_ZERO:
                        $this->stat_data[$key] = 0;
                        break;
                    default:
                        $result = false;
                }
            }
        }
        sort($this->stat_data);
        return $result;
    }

References ILIAS\LTI\ToolProvider\$key, NAN_HANDLING_REMOVE, and NAN_HANDLING_ZERO.

Referenced by setData().

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Field Documentation

$nan_handling

ilStatistics::$nan_handling

Definition at line 42 of file class.ilStatistics.php.

Referenced by __construct(), getNANHandling(), and setNANHandling().

$stat_data

ilStatistics::$stat_data

Definition at line 50 of file class.ilStatistics.php.

Referenced by getData(), and setData().

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The documentation for this class was generated from the following file:

• Modules/Test/classes/class.ilStatistics.php