org.apache.poi.ss.formula.functions.Covar Maven / Gradle / Ivy

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package org.apache.poi.ss.formula.functions;

import org.apache.commons.math3.stat.correlation.Covariance;
import org.apache.poi.ss.formula.OperationEvaluationContext;
import org.apache.poi.ss.formula.eval.ErrorEval;
import org.apache.poi.ss.formula.eval.EvaluationException;
import org.apache.poi.ss.formula.eval.NumberEval;
import org.apache.poi.ss.formula.eval.ValueEval;

import java.util.List;

import static org.apache.poi.ss.formula.functions.ArrayFunctionUtils.getNumberArrays;

/**
 * Implementation for Excel COVAR() and COVARIANCE.P() functions.
 * 
 *   Syntax:
 COVAR (array1, array2)

 * 
 * @see COVAR
 * @see COVARIANCE.P
 */
public class Covar extends Fixed2ArgFunction implements FreeRefFunction {

    public static final Covar instanceP = new Covar(false);
    public static final Covar instanceS = new Covar(true);

    private final boolean sampleBased;

    private Covar(boolean sampleBased) {
        this.sampleBased = sampleBased;
    }

    @Override
    public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1) {
        try {
            final List arrays = getNumberArrays(arg0, arg1);
            final Covariance covar = new Covariance();
            final double result = covar.covariance(
                    arrays.get(0).toArray(), arrays.get(1).toArray(), sampleBased);
            return new NumberEval(result);
        } catch (EvaluationException e) {
            return e.getErrorEval();
        } catch (Exception e) {
            return ErrorEval.NA;
        }
    }

    @Override
    public ValueEval evaluate(ValueEval[] args, OperationEvaluationContext ec) {
        if (args.length != 2) {
            return ErrorEval.VALUE_INVALID;
        }
        return evaluate(ec.getRowIndex(), ec.getColumnIndex(), args[0], args[1]);
    }
}