Class StandardDeviationVisitor

  • All Implemented Interfaces:
    FeatureVisitor, FeatureAttributeVisitor, FeatureCalc

    public class StandardDeviationVisitor
    extends Object
    implements FeatureCalc, FeatureAttributeVisitor
    Determines the standard deviation.
                |  1   ---
     Std dev =  | ___  \   ( x - mean ) ^ 2
               \|  N   /__
    aka std dev = sqrt((sum((x-mean)^2))/N) where N is the number of samples.

    It uses the rolling variance algorithm described here:

    Cory Horner, Refractions Research Inc., Andrea Aime, GeoSolutions
    • Constructor Detail

      • StandardDeviationVisitor

        public StandardDeviationVisitor​(Expression expr)
        Constructs a standard deviation visitor based on the specified expression
    • Method Detail

      • getExpression

        public Expression getExpression()
      • setValue

        public void setValue​(Object value)
      • getResult

        public CalcResult getResult()
        Description copied from interface: FeatureCalc
        Returns the result of the calculation as a handy object which can be merged and modified.
        Specified by:
        getResult in interface FeatureCalc
        the results of the calculation
      • visit

        public void visit​(Feature feature)
        Description copied from interface: FeatureVisitor
        Visit the provided feature.

        Please consult the documentation for the FeatureCollection you are visiting to learn more - the provided feature may be invalid, or read only.

        Specified by:
        visit in interface FeatureVisitor
      • reset

        public void reset()
      • getMean

        public double getMean()
        mean value generated when calcualting standard deviation
      • getNaNCount

        public int getNaNCount()
        the number of features which returned a NaN
      • getNullCount

        public int getNullCount()
        the number of features which returned a null