决策树 c++实现

决策树c++实现

Posted by 高庆东 on August 1, 2018

决策树c++

#include <iostream>
#include <fstream>
#include <math.h>
#include <string>
using namespace std;

#define ROW 14
#define COL 5
#define log2 0.69314718055

typedef struct TNode
{
	char data[15];
	char weight[15]; 
	TNode * firstchild,*nextsibling;
}*tree;

typedef struct LNode
{
	char  OutLook[15];
	char  Temperature[15];
	char  Humidity[15];
	char  Wind[15];
	char  PlayTennis[5];

	LNode *next;
}*link;
typedef struct AttrNode
{
	char   attributes[15];//属性
	int	   attr_Num;//属性的个数

	AttrNode *next;
}*Attributes;

数据

char * Examples[ROW][COL] = {//"OverCast","Cool","High","Strong","No",
					//	"Rain","Hot","Normal","Strong","Yes",
						"Sunny","Hot","High","Weak","No",
						  "Sunny","Hot","High","Strong","No",
						  "OverCast","Hot","High","Weak","Yes",
						  "Rain","Mild","High","Weak","Yes",
						"Rain","Cool","Normal","Weak","Yes",
						"Rain","Cool","Normal","Strong","No",
						"OverCast","Cool","Normal","Strong","Yes",
						"Sunny","Mild","High","Weak","No",
						"Sunny","Cool","Normal","Weak","Yes",
						"Rain","Mild","Normal","Weak","Yes",
						"Sunny","Mild","Normal","Strong","Yes",
						"OverCast","Mild","Normal","Strong","Yes",
						"OverCast","Hot","Normal","Weak","Yes",
						"Rain","Mild","High","Strong","No"
						};
char * Attributes_kind[4] = {"OutLook","Temperature","Humidity","Wind"};
int	   Attr_kind[4] = {3,3,2,2};

char * OutLook_kind[3] = {"Sunny","OverCast","Rain"};
char * Temperature_kind[3] = {"Hot","Mild","Cool"};
char * Humidity_kind[2] = {"High","Normal"};
char * Wind_kind[2] = {"Weak","Strong"};

/*int i_Exampple[14][5] = {0,0,0,0,1,
						0,0,0,1,1,
						1,0,0,1,0,
						2,1,0,0,0,
						2,2,1,0,0,
						2,2,1,1,1,
						1,2,1,1,0,
						0,1,0,0,1,
						0,2,1,0,0,
						2,1,1,0,0,
						0,1,1,1,0,
						1,1,1,1,0,
						1,1,1,0,0,
						2,1,0,0,1
						};*/
void treelists(tree T);
void InitAttr(Attributes &attr_link,char * Attributes_kind[],int Attr_kind[]);
void InitLink(link &L,char * Examples[][COL]);
void ID3(tree &T,link L,link Target_Attr,Attributes attr);
void PN_Num(link L,int &positve,int &negative);
double Gain(int positive,int negative,char * atrribute,link L,Attributes attr_L);

主函数

void main()
{
	link LL,p;
	Attributes attr_L,q;

	tree T;
	T = new TNode;
	T->firstchild = T->nextsibling = NULL;
	strcpy(T->weight,"");
	strcpy(T->data,"");

	attr_L = new AttrNode;
	attr_L->next = NULL;

	LL = new LNode;
	LL->next = NULL;

	//成功建立两个链表
	InitLink(LL,Examples);
	InitAttr(attr_L,Attributes_kind,Attr_kind);

	ID3(T,LL,NULL,attr_L);

	cout<<"决策树以广义表形式输出如下："<<endl;
	treelists(T);//以广义表的形式输出树
//	cout<<Gain(9,5,"OutLook",LL,attr_L)<<endl;

	cout<<endl;
	system("pause");
}

决策函数

//以广义表的形式输出树
void treelists(tree T)
{
	tree p;

	if(!T)
		return;
	cout<<"{"<<T->weight<<"}";
	cout<<T->data;

	p = T->firstchild;
	if (p)
	{
		cout<<"(";
		while (p)
		{
			treelists(p);
			p = p->nextsibling;
			if (p)cout<<',';
		}
		cout<<")";
	}
}
void InitAttr(Attributes &attr_link,char * Attributes_kind[],int Attr_kind[])
{
	Attributes p;

	for (int i =0;i < 4;i++)
	{
		p = new AttrNode;
		p->next = NULL;
		
		strcpy(p->attributes,Attributes_kind[i]);
		p->attr_Num = Attr_kind[i];

		p->next = attr_link->next;
		attr_link->next = p;
	}
}
void InitLink(link &LL,char * Examples[][COL])
{
	link p;	

	for (int i = 0;i < ROW;i++)
	{
		p = new LNode;
		p->next = NULL;

		strcpy(p->OutLook,Examples[i][0]);
		strcpy(p->Temperature,Examples[i][1]);
		strcpy(p->Humidity,Examples[i][2]);
		strcpy(p->Wind,Examples[i][3]);
		strcpy(p->PlayTennis,Examples[i][4]);

		p->next = LL->next;
		LL->next = p;	
	}
}
void PN_Num(link L,int &positve,int &negative)
{
	positve = 0;
	negative = 0;
	link p;
	
	p = L->next;
	while (p)
	{
		if (strcmp(p->PlayTennis,"No") == 0)
			negative++;
		else if(strcmp(p->PlayTennis,"Yes") == 0)
			positve++;

		p = p->next;
	}		
}

//计算信息增益
//link L: 样本集合S
//attr_L：属性集合
double Gain(int positive,int negative,char * atrribute,link L,Attributes attr_L)
{
	int atrr_kinds;//每个属性中的值的个数

	Attributes p = attr_L->next;
	link q = L->next;

	int attr_th = 0;//第几个属性
	while (p)
	{
		if (strcmp(p->attributes,atrribute) == 0)
		{
			atrr_kinds = p->attr_Num;		
			break;
		}
		p = p->next;
		attr_th++;
	}

	double entropy,gain=0;

	double p1 = 1.0*positive/(positive + negative);
	double p2 = 1.0*negative/(positive + negative);

	entropy = -p1*log(p1)/log2 - p2*log(p2)/log2;//集合熵
	gain = entropy;

	//获取每个属性值在训练样本中出现的个数
	//获取每个属性值所对应的正例和反例的个数
	
	//声明一个3*atrr_kinds的数组
	int ** kinds= new int * [3];
	for (int j =0;j < 3;j++)
	{
		kinds[j] = new int[atrr_kinds];//保存每个属性值在训练样本中出现的个数
	}

	//初始化
	for (int j = 0;j< 3;j++)
	{
		for (int i =0;i < atrr_kinds;i++)
		{
			kinds[j][i] = 0;
		}
	}
	while (q)
	{
		if (strcmp("OutLook",atrribute) == 0)
		{
			for (int i = 0;i < atrr_kinds;i++)
			{
				if(strcmp(q->OutLook,OutLook_kind[i]) == 0)
				{
					kinds[0][i]++;

					if(strcmp(q->PlayTennis,"Yes") == 0)
						kinds[1][i]++;
					else
						kinds[2][i]++;
				}
			}
		}
		else if (strcmp("Temperature",atrribute) == 0)
		{
			for (int i = 0;i < atrr_kinds;i++)
			{
				if(strcmp(q->Temperature,Temperature_kind[i]) == 0)
				{
					kinds[0][i]++;

					if(strcmp(q->PlayTennis,"Yes") == 0)
						kinds[1][i]++;
					else
						kinds[2][i]++;
				}
			}
		}
		else if (strcmp("Humidity",atrribute) == 0)
		{
			for (int i = 0;i < atrr_kinds;i++)
			{
				if(strcmp(q->Humidity,Humidity_kind[i]) == 0)
				{
					kinds[0][i]++;

					if(strcmp(q->PlayTennis,"Yes") == 0)
						kinds[1][i]++;// 
					else
						kinds[2][i]++;
				}
			}
		}
		else if (strcmp("Wind",atrribute) == 0)
		{
			for (int i = 0;i < atrr_kinds;i++)
			{
				if(strcmp(q->Wind,Wind_kind[i]) == 0)
				{
					kinds[0][i]++;

					if(strcmp(q->PlayTennis,"Yes") == 0)
						kinds[1][i]++;
					else
						kinds[2][i]++;
				}
			}
		}
		q = q->next;
	}

	//计算信息增益
	double * gain_kind = new double[atrr_kinds];
	int positive_kind = 0,negative_kind = 0;

	for (int j = 0;j < atrr_kinds;j++)
	{
		if (kinds[0][j] != 0 && kinds[1][j] != 0 && kinds[2][j] != 0)
		{
			p1 = 1.0*kinds[1][j]/kinds[0][j];
			p2 = 1.0*kinds[2][j]/kinds[0][j];
			
			gain_kind[j] = -p1*log(p1)/log2-p2*log(p2)/log2;
			
			gain = gain - (1.0*kinds[0][j]/(positive + negative))*gain_kind[j];
		}
		else
			gain_kind[j] = 0;
	}
	return gain;
}

//在ID3算法中的训练样本子集合与属性子集合的链表需要进行清空
void FreeLink(link &Link)
{
	link p,q;
	
	p = Link->next;
	
	Link->next = NULL;
	while (p)
	{
		q = p;
		p = p->next;
		free(q);
	}
}
void ID3(tree &T,link L,link Target_Attr,Attributes attr)
{
	Attributes p,max,attr_child,p1;
	link q,link_child,q1;
	tree r,tree_p;
	
	int positive =0,negative =0;

	PN_Num(L,positive,negative);

	//初始化两个子集合
	attr_child = new AttrNode;
	attr_child->next = NULL;

	link_child = new LNode;
	link_child->next = NULL;

	if (positive == 0)//全是反例
	{
		strcpy(T->data,"No");
		return;
	}
	else if( negative == 0)//全是正例
	{
		strcpy(T->data,"Yes");
		return;
	}
	
	p = attr->next; //属性链表

	double gain,g = 0;

	/************************************************************************/
	/* 建立属性子集合与训练样本子集合有两个方案：
		一：在原来链表的基础上进行删除；
		二：另外申请空间进行存储子集合；
		采用第二种方法虽然浪费了空间，但也省了很多事情，避免了变量之间的应用混乱
	*/
	/************************************************************************/

	if(p)
	{
		while (p)
		{
			gain = Gain(positive,negative,p->attributes,L,attr);
			cout<<p->attributes<<"  "<<gain<<endl;
			if(gain > g)
			{
				g = gain;
				max = p;//寻找信息增益最大的属性
			}
			p = p->next;
		}
		strcpy(T->data,max->attributes);//增加决策树的节点
		
		cout<<"信息增益最大的属性：max->attributes = "<<max->attributes<<endl<<endl;
		//下面开始建立决策树

		//创建属性子集合
		p = attr->next;
		while (p)
		{
			if (strcmp(p->attributes,max->attributes) != 0)
			{
				p1 = new AttrNode;
				strcpy(p1->attributes,p->attributes);
				p1->attr_Num = p->attr_Num;
				p1->next = NULL;

				p1->next = attr_child->next;
				attr_child->next = p1;		
			}
			p = p->next;
		}
		
		//需要区分出是哪一种属性
		//建立每一层的第一个节点
		if (strcmp("OutLook",max->attributes) == 0)
		{
			r = new TNode;
			r->firstchild = r->nextsibling = NULL;
			strcpy(r->weight,OutLook_kind[0]);
			T->firstchild = r;
			//获取与属性值相关的训练样例Example(vi),建立一个新的训练样本链表link_child
			q = L->next;
			while (q)
			{
				if (strcmp(q->OutLook,OutLook_kind[0]) == 0)
				{
					q1 = new LNode;
					strcpy(q1->OutLook,q->OutLook);
					strcpy(q1->Humidity,q->Humidity);
					strcpy(q1->Temperature,q->Temperature);
					strcpy(q1->Wind,q->Wind);
					strcpy(q1->PlayTennis,q->PlayTennis);
					q1->next = NULL;
					
					q1->next = link_child->next;
					link_child->next = q1;
				}
				q = q->next;
			}
		}
		else if (strcmp("Temperature",max->attributes) == 0)
		{
			r = new TNode;
			r->firstchild = r->nextsibling = NULL;
			strcpy(r->weight,Temperature_kind[0]);
			T->firstchild = r;
			//获取与属性值相关的训练样例Example(vi),建立一个新的训练样本链表link_child
			q = L->next;
			while (q)
			{
				if (strcmp(q->Temperature,Temperature_kind[0]) == 0)
				{
					q1 = new LNode;
					strcpy(q1->OutLook,q->OutLook);
					strcpy(q1->Humidity,q->Humidity);
					strcpy(q1->Temperature,q->Temperature);
					strcpy(q1->Wind,q->Wind);
					strcpy(q1->PlayTennis,q->PlayTennis);
					q1->next = NULL;
					
					q1->next = link_child->next;
					link_child->next = q1;
				}
				q = q->next;
			}
		}
		else if (strcmp("Humidity",max->attributes) == 0)
		{
			r = new TNode;
			r->firstchild = r->nextsibling = NULL;
			strcpy(r->weight,Humidity_kind[0]);
			T->firstchild = r;
			//获取与属性值相关的训练样例Example(vi),建立一个新的训练样本链表link_child
			q = L->next;
			while (q)
			{
				if (strcmp(q->Humidity,Humidity_kind[0]) == 0)
				{
					q1 = new LNode;
					strcpy(q1->OutLook,q->OutLook);
					strcpy(q1->Humidity,q->Humidity);
					strcpy(q1->Temperature,q->Temperature);
					strcpy(q1->Wind,q->Wind);
					strcpy(q1->PlayTennis,q->PlayTennis);
					q1->next = NULL;
					
					q1->next = link_child->next;
					link_child->next = q1;
				}
				q = q->next;
			}
		}
		else if (strcmp("Wind",max->attributes) == 0)
		{
			r = new TNode;
			r->firstchild = r->nextsibling = NULL;
			strcpy(r->weight,Wind_kind[0]);

			T->firstchild = r;
			//获取与属性值相关的训练样例Example(vi),建立一个新的训练样本链表link_child
			q = L->next;
			while (q)
			{
				if (strcmp(q->Wind,Wind_kind[0]) == 0)
				{
					q1 = new LNode;
					strcpy(q1->OutLook,q->OutLook);
					strcpy(q1->Humidity,q->Humidity);
					strcpy(q1->Temperature,q->Temperature);
					strcpy(q1->Wind,q->Wind);
					strcpy(q1->PlayTennis,q->PlayTennis);
					q1->next = NULL;
					
					q1->next = link_child->next;
					link_child->next = q1;
				}
				q = q->next;
			}
		}

		int p = 0,n = 0;
		PN_Num(link_child,p,n);
		if (p != 0 && n != 0)
		{
			ID3(T->firstchild,link_child,Target_Attr,attr_child);
			FreeLink(link_child);
		}
		else if(p == 0)
		{
			strcpy(T->firstchild->data,"No");
			FreeLink(link_child);
			//	strcpy(T->firstchild->data,q1->PlayTennis);//----此处应该需要修改----:)
		}
		else if(n == 0)
		{
			strcpy(T->firstchild->data,"Yes");
			FreeLink(link_child);
		}

		//建立每一层上的其他节点
		tree_p = T->firstchild;
		for (int i = 1;i < max->attr_Num;i++)
		{
			//需要区分出是哪一种属性
			if (strcmp("OutLook",max->attributes) == 0)
			{
				r = new TNode;
				r->firstchild = r->nextsibling = NULL;
				strcpy(r->weight,OutLook_kind[i]);
				tree_p->nextsibling = r;
				//获取与属性值相关的训练样例Example(vi),建立一个新的训练样本链表link_child
				q = L->next;
				while (q)
				{
					if (strcmp(q->OutLook,OutLook_kind[i]) == 0)
					{
						q1 = new LNode;
						strcpy(q1->OutLook,q->OutLook);
						strcpy(q1->Humidity,q->Humidity);
						strcpy(q1->Temperature,q->Temperature);
						strcpy(q1->Wind,q->Wind);
						strcpy(q1->PlayTennis,q->PlayTennis);
						q1->next = NULL;

						q1->next = link_child->next;
						link_child->next = q1;
					}
					q = q->next;
				}
			}
			else if (strcmp("Temperature",max->attributes) == 0)
			{
				r = new TNode;
				r->firstchild = r->nextsibling = NULL;
				strcpy(r->weight,Temperature_kind[i]);
				tree_p->nextsibling = r;
				//获取与属性值相关的训练样例Example(vi),建立一个新的训练样本链表link_child
				q = L->next;
				while (q)
				{
					if (strcmp(q->Temperature,Temperature_kind[i]) == 0)
					{
						q1 = new LNode;
						strcpy(q1->OutLook,q->OutLook);
						strcpy(q1->Humidity,q->Humidity);
						strcpy(q1->Temperature,q->Temperature);
						strcpy(q1->Wind,q->Wind);
						strcpy(q1->PlayTennis,q->PlayTennis);
						q1->next = NULL;
						
						q1->next = link_child->next;
						link_child->next = q1;
					}
					q = q->next;
				}
				
			}
			else if (strcmp("Humidity",max->attributes) == 0)
			{
				r = new TNode;
				r->firstchild = r->nextsibling = NULL;
				strcpy(r->weight,Humidity_kind[i]);
				tree_p->nextsibling = r;
				//获取与属性值相关的训练样例Example(vi),建立一个新的训练样本链表link_child
				q = L->next;
				while (q)
				{
					if (strcmp(q->Humidity,Humidity_kind[i]) == 0)
					{
						q1 = new LNode;
						strcpy(q1->OutLook,q->OutLook);
						strcpy(q1->Humidity,q->Humidity);
						strcpy(q1->Temperature,q->Temperature);
						strcpy(q1->Wind,q->Wind);
						strcpy(q1->PlayTennis,q->PlayTennis);
						q1->next = NULL;
						
						q1->next = link_child->next;
						link_child->next = q1;
					}
					q = q->next;
				}
			}
			else if (strcmp("Wind",max->attributes) == 0)
			{
				r = new TNode;
				r->firstchild = r->nextsibling = NULL;
				strcpy(r->weight,Wind_kind[i]);
				tree_p->nextsibling = r;
				//获取与属性值相关的训练样例Example(vi),建立一个新的训练样本链表link_child
				q = L->next;
				while (q)
				{
					if (strcmp(q->Wind,Wind_kind[i]) == 0)
					{
						q1 = new LNode;
						strcpy(q1->OutLook,q->OutLook);
						strcpy(q1->Humidity,q->Humidity);
						strcpy(q1->Temperature,q->Temperature);
						strcpy(q1->Wind,q->Wind);
						strcpy(q1->PlayTennis,q->PlayTennis);
						q1->next = NULL;
						
						q1->next = link_child->next;
						link_child->next = q1;
					}
					q = q->next;
				}
			}
			int p = 0,n = 0;
			PN_Num(link_child,p,n);
			if (p != 0 && n != 0)
			{
				ID3(tree_p->nextsibling,link_child,Target_Attr,attr_child);
				FreeLink(link_child);
			}
			else if(p == 0)
			{
				strcpy(tree_p->nextsibling->data,"No");
				FreeLink(link_child);
			}
			else if(n == 0)
			{
				strcpy(tree_p->nextsibling->data,"Yes");
				FreeLink(link_child);
			}

			tree_p = tree_p->nextsibling;//建立所有的孩子结点
		}//建立决策树结束
	}
	else
	{
		q = L->next;
		strcpy(T->data,q->PlayTennis);
		return;//这个地方要赋以训练样本Example中最普遍的Target_attributes的值
	}
}
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