er.extensions.foundation
Class ERXArrayUtilities.StandardDeviationOperator

java.lang.Object
  er.extensions.foundation.ERXArrayUtilities.StandardDeviationOperator

All Implemented Interfaces:

com.webobjects.foundation.NSArray.Operator

Enclosing class:

ERXArrayUtilities

public static class ERXArrayUtilities.StandardDeviationOperator
extends java.lang.Object
implements com.webobjects.foundation.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

ERXArrayUtilities.StandardDeviationOperator(boolean isPopulation)

Method Summary

java.lang.Object

compute(com.webobjects.foundation.NSArray<?> array, java.lang.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

ERXArrayUtilities.StandardDeviationOperator

public ERXArrayUtilities.StandardDeviationOperator(boolean isPopulation)

Method Detail

compute

public java.lang.Object compute(com.webobjects.foundation.NSArray<?> array,
                                java.lang.String keypath)

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

Specified by:

compute in interface com.webobjects.foundation.NSArray.Operator

Parameters:

array - array to be checked.

keypath - path to numeric values

Returns:

standard deviation value