向量余弦值(Cosine)(C#)

接前面一篇TF-IDF的代码,用其结果来计算出向量的余弦值的代码

using System;

using System.Collections.Generic;

using System.Text;



namespace Cluster

{

    static class Cosine

    {

        /// <summary>

        /// 计算向量余弦值

        /// </summary>

        /// <param name="vector1"></param>

        /// <param name="vector2"></param>

        public static double Calculate(Dictionary<int, double> vector1, Dictionary<int, double> vector2)

        {

            double dotProduct = CalcDotProduct(vector1, vector2);

            double length1 = CalcLength(vector1);

            double length2 = CalcLength(vector2);

            double cosine = dotProduct / (length1 * length2);



            return cosine;

        }



        /// <summary>

        /// 计算向量长度(vector length)

        /// </summary>

        /// <param name="vector"></param>

        /// <returns></returns>

        private static double CalcLength(Dictionary<int, double> vector)

        {

            double length = 0;

            foreach (KeyValuePair<int, double> kvp in vector)

            {

                length += Math.Pow(kvp.Value, 2);

            }

            return Math.Sqrt(length);

        }



        /// <summary>

        /// 计算向量点积(dot product)/内积(inner product)

        /// </summary>

        /// <param name="vector1"></param>

        /// <param name="vector2"></param>

        /// <returns></returns>

        private static double CalcDotProduct(Dictionary<int, double> vector1, Dictionary<int, double> vector2)

        {

            double dotProduct = 0;

            foreach (KeyValuePair<int, double> kvp in vector1)

            {

                if (vector2.ContainsKey(kvp.Key))

                {

                    dotProduct += kvp.Value * vector2[kvp.Key];

                }

            }

            return dotProduct;

        }

    }

}