Variance (GenericNamedArraylist function)

Calculate variance of items or function of items (FloatNamedArraylist, NamedArraylist, and UnicodeNamedArraylist classes)

[Introduced in Sirius Mods 7.8]

This method returns by default the variance of the values of the items in the collection, or it returns the variance of the items after a specified function has been applied to them.

The variance is the "mean standard deviation" of the values of the items in the collection, the average of the squares of the deviations of the value of each item from the mean of all the items.

Syntax

%number = anyNal:Variance[( [itemFunction])]

Syntax terms

%number	A Float variable to contain the numeric result.
anyNal	An FloatNamedArraylist, NamedArraylist, or UnicodeNamedArraylist object.
itemFunction	A function that operates on the type of the items in the collection. It may be a local method or method variable or a class member (Variable, Property), and it must return an intrinsic (probably Float) value. The default itemFunction value is the special identity function, This, which simply returns the item value.

Usage notes

• The optional itemFunction parameter lets you further manipulate the collection item values before calculating the average. If your collection items are not intrinsic values, you must specify a function that can map the item values to intrinsic values or the method will fail.

  For an example, see the Arraylist Variance "Usage notes" section.

Examples

b %nl is namedarrayList of float %nl = new %nl('April') = 3000 %nl('May') = 5000 %nl('June') = 8000 printText {~} is {%nl:variance} end

The result is:

%nl:variance is 4222222.22222222

See also

Arraylist class FloatNamedArraylist class NamedArraylist class UnicodeNamedArraylist class	List of Arraylist methods List of FloatNamedArraylist methods List of NamedArraylist methods List of UnicodeNamedArraylist methods List of Collection methods	Arraylist methods syntax FloatNamedArraylist methods syntax NamedArraylist methods syntax UnicodeNamedArraylist methods syntax
Notation conventions for methods