mathx.java

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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements.  See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License.  You may obtain a copy of the License at
*
*     http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
 * Created on May 19, 2005
 *
 */
package org.apache.poi.hssf.record.formula.functions;



/**
 * @author Amol S. Deshmukh < amolweb at ya hoo dot com >
 * This class is an extension to the standard math library
 * provided by java.lang.Math class. It follows the Math class
 * in that it has a private constructor and all static methods.
 */
public final class MathX {

    
    private MathX() {}
    
    
    /**
     * Returns a value rounded to p digits after decimal.
     * If p is negative, then the number is rounded to
     * places to the left of the decimal point. eg. 
     * 10.23 rounded to -1 will give: 10. If p is zero,
     * the returned value is rounded to the nearest integral
     * value.
     * <p>If n is negative, the resulting value is obtained
     * as the round value of absolute value of n multiplied
     * by the sign value of n (@see MathX.sign(double d)). 
     * Thus, -0.6666666 rounded to p=0 will give -1 not 0.
     * <p>If n is NaN, returned value is NaN.
     * @param n
     * @param p
     * @return
     */
    public static double round(double n, int p) {
        double retval;
        
        if (Double.isNaN(n) || Double.isInfinite(n)) {
            retval = Double.NaN;
        }
        else {
            if (p != 0) {
                double temp = Math.pow(10, p);
                retval = Math.round(n*temp)/temp;
            }
            else {
                retval = Math.round(n);
            }
        }
        
        return retval;
    }

    /**
     * Returns a value rounded-up to p digits after decimal.
     * If p is negative, then the number is rounded to
     * places to the left of the decimal point. eg. 
     * 10.23 rounded to -1 will give: 20. If p is zero,
     * the returned value is rounded to the nearest integral
     * value.
     * <p>If n is negative, the resulting value is obtained
     * as the round-up value of absolute value of n multiplied
     * by the sign value of n (@see MathX.sign(double d)). 
     * Thus, -0.2 rounded-up to p=0 will give -1 not 0.
     * <p>If n is NaN, returned value is NaN.
     * @param n
     * @param p
     * @return
     */
    public static double roundUp(double n, int p) {
        double retval;
        
        if (Double.isNaN(n) || Double.isInfinite(n)) {
            retval = Double.NaN;
        }
        else {
            if (p != 0) {
                double temp = Math.pow(10, p);
                double nat = Math.abs(n*temp);
                
                retval = sign(n) * 
                    ((nat == (long) nat)
                            ? nat / temp
                            : Math.round(nat + 0.5) / temp);
            }
            else {
                double na = Math.abs(n);
                retval = sign(n) * 
                    ((na == (long) na)
                        ? na
                        : (long) na + 1);
            }
        }
        
        return retval;
    }

    /**
     * Returns a value rounded to p digits after decimal.
     * If p is negative, then the number is rounded to
     * places to the left of the decimal point. eg. 
     * 10.23 rounded to -1 will give: 10. If p is zero,
     * the returned value is rounded to the nearest integral
     * value.
     * <p>If n is negative, the resulting value is obtained
     * as the round-up value of absolute value of n multiplied
     * by the sign value of n (@see MathX.sign(double d)). 
     * Thus, -0.8 rounded-down to p=0 will give 0 not -1.
     * <p>If n is NaN, returned value is NaN.
     * @param n
     * @param p
     * @return
     */
    public static double roundDown(double n, int p) {
        double retval;
        
        if (Double.isNaN(n) || Double.isInfinite(n)) {
            retval = Double.NaN;
        }
        else {
            if (p != 0) {
                double temp = Math.pow(10, p);
                retval = sign(n) * Math.round((Math.abs(n)*temp) - 0.5)/temp;
            }
            else {
                retval = (long) n;
            }
        }
        
        return retval;
    }
    
    
    /**
     * If d < 0, returns short -1
     * <br/>
     * If d > 0, returns short 1
     * <br/>
     * If d == 0, returns short 0 
     * <p> If d is NaN, then 1 will be returned. It is the responsibility
     * of caller to check for d isNaN if some other value is desired.
     * @param d
     * @return
     */
    public static short sign(double d) {
        return (short) ((d == 0)
                ? 0
                : (d < 0)
                        ? -1
                        : 1);
    }
   
    /**
     * average of all values
     * @param values
     * @return
     */
    public static double average(double[] values) {
        double ave = 0;
        double sum = 0;
        for (int i=0, iSize=values.length; i<iSize; i++) {
            sum += values[i];
        }
        ave = sum / values.length;
        return ave;
    }
    
    
    /**
     * sum of all values
     * @param values
     * @return
     */
    public static double sum(double[] values) {
        double sum = 0;
        for (int i=0, iSize=values.length; i<iSize; i++) {
            sum += values[i];
        }
        return sum;
    }
    
    /**
     * sum of squares of all values
     * @param values
     * @return
     */
    public static double sumsq(double[] values) {
        double sumsq = 0;
        for (int i=0, iSize=values.length; i<iSize; i++) {
            sumsq += values[i]*values[i];
        }
        return sumsq;
    }
    
    
    /**
     * product of all values
     * @param values
     * @return
     */
    public static double product(double[] values) {
        double product = 0;
        if (values!=null && values.length > 0) {
            product = 1;
            for (int i=0, iSize=values.length; i<iSize; i++) {
                product *= values[i];
            }
        }
        return product;
    }
    
    /**
     * min of all values. If supplied array is zero length,
     * Double.POSITIVE_INFINITY is returned.
     * @param values
     * @return
     */
    public static double min(double[] values) {
        double min = Double.POSITIVE_INFINITY;
        for (int i=0, iSize=values.length; i<iSize; i++) {
            min = Math.min(min, values[i]);
        }
        return min;
    }

    /**
     * min of all values. If supplied array is zero length,
     * Double.NEGATIVE_INFINITY is returned.
     * @param values
     * @return
     */
    public static double max(double[] values) {
        double max = Double.NEGATIVE_INFINITY;
        for (int i=0, iSize=values.length; i<iSize; i++) {
            max = Math.max(max, values[i]);
        }
        return max;
    }

    /**
     * Note: this function is different from java.lang.Math.floor(..).
     * <p>
     * When n and s are "valid" arguments, the returned value is: Math.floor(n/s) * s;
     * <br/>
     * n and s are invalid if any of following conditions are true:
     * <ul>
     * <li>s is zero</li>
     * <li>n is negative and s is positive</li>
     * <li>n is positive and s is negative</li>
     * </ul>
     * In all such cases, Double.NaN is returned.
     * @param n
     * @param s
     * @return
     */
    public static double floor(double n, double s) {
        double f;
        
        if ((n<0 && s>0) || (n>0 && s<0) || (s==0 && n!=0)) {
            f = Double.NaN;
        }
        else {
            f = (n==0 || s==0) ? 0 : Math.floor(n/s) * s;
        }
        
        return f;
    }
    
    /**
     * Note: this function is different from java.lang.Math.ceil(..).
     * <p>
     * When n and s are "valid" arguments, the returned value is: Math.ceiling(n/s) * s;
     * <br/>
     * n and s are invalid if any of following conditions are true:
     * <ul>
     * <li>s is zero</li>