4.1.3.2.5 SampleVariance

SampleVariance function

Prototype:	function SampleVariance (TableOrLayer :TObjectWrapper; const AttributeName :string; const NullAsZero :boolean) : extended;
Description:	Calculates variance of a specific attribute
Syntax:	variable := SampleVariance (tab, AttributeName, NullAsZero);
	Part	Description
	variable	A variable declared as type of extended
	tab	Table containing source variables
	AttributeName	Attribute of source table containing data to enter calculations
	NullAsZero	Boolean expression defining whether to exclude null (false) entries or replace nulls with zeros (true)

Return value:	Variance

Example:

Task:

Calculate variance of DBH.

Data stored in the database.

Script:

var

tab : TTableWrapper;

attributeName: string;

nullAsZero: boolean;

x: extended;

begin

tab:= Trees.table;

attributeName:= 'DBH_mm';

nullAsZero:= false; // dont want calculate with a null value

x:= SampleVariance(tab, attributeName, nullAsZero);

ShowMessage(FloatToStr(x));

end.

Output in Field-Map Data Collector:

variance of DBH