@Override
    public double value(int indexAttribute) {
        int location = locateIndex(indexAttribute);
        if ((location >= 0) && (indexValues[location] == indexAttribute)) {
            return attributeValues[location];
        } else {
            // returns a NaN value which represents missing values instead of a 0 (zero)
            return Double.NaN;
        }
    }
@ Override public double value ( int indexAttribute ) { int location = locateIndex ( indexAttribute ) ; if ( ( location >= 0 ) && ( indexValues [ location ] == indexAttribute ) ) { return attributeValues [ location ] ; } else { return Double . NaN ; } }
Value of the attribute in the indexAttribute position.
If this value is absent, a NaN value (marker of missing value)
is returned, otherwise this method returns the actual value.

@param indexAttribute the index attribute
@return the double