er.extensions.foundation

Class ERXArrayUtilities.StandardDeviationOperator

java.lang.Object

er.extensions.foundation.ERXArrayUtilities.StandardDeviationOperator

All Implemented Interfaces:

NSArray.Operator

Enclosing class:

ERXArrayUtilities

public static class ERXArrayUtilities.StandardDeviationOperator
extends Object
implements NSArray.Operator

Define an NSArray.Operator for the key stdDev and popStdDev.

This allows for key value paths like:

• myArray.valueForKey("@stdDev.payment.amount");
• myArray.valueForKey("payment.@stdDev.amount");
• myArray.valueForKey("payment.amount.@stdDev");

All three of these examples will return the same value, which in this case is the standard deviation of the amounts. The standard deviation is a measure of the dispersion of a sample of numbers. The population standard deviation is used if you have the values for an entire population.

The standard deviation operator applies to the array of objects to its left if it is the last key in the path. Otherwise it applies to the end of the keypath to its right. It should not be followed by an array or any other array operators. This is because it does not call valueForKeyPath on the array to its left, but instead loops through the values of the array to its left, calling valueForKeyPath on the individual array values instead. This behavior is consistent with Apple's standard NSArray operators.

Constructor Summary

Constructors

Constructor and Description
StandardDeviationOperator(boolean isPopulation)

Method Summary

Modifier and Type	Method and Description
Object	compute(NSArray array, String keypath) returns the standard deviation value for the values of the keypath.

Methods inherited from class java.lang.Object

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

Constructor Detail

StandardDeviationOperator

public StandardDeviationOperator(boolean isPopulation)

Method Detail

compute

public Object compute(NSArray array,
                      String keypath)

returns the standard deviation value for the values of the keypath.

Specified by:

compute in interface NSArray.Operator

Parameters:

array - array to be checked.

keypath - path to numeric values

Returns:

standard deviation value