diff --git a/README.md b/README.md
index 923d4a8..0f1b056 100644
--- a/README.md
+++ b/README.md
@@ -38,7 +38,9 @@ MachineLearning
 
 - **logistic regression**
 
-      基于python+numpy实现了logistic回归（二类别），详细的介绍：[文章链接](http://blog.csdn.net/u012162613/article/details/41844495)
+	  - 基于C++以及线性代数库Eigen实现的logistic回归，[代码]()
+
+      - 基于python+numpy实现了logistic回归（二类别），详细的介绍：[文章链接](http://blog.csdn.net/u012162613/article/details/41844495)
 
 - **ManifoldLearning**
 
diff --git a/logistic regression/use_cpp_and_eigen/README.md b/logistic regression/use_cpp_and_eigen/README.md
new file mode 100644
index 0000000..4b581d8
--- /dev/null
+++ b/logistic regression/use_cpp_and_eigen/README.md	
@@ -0,0 +1,52 @@
+###A tiny C++ implement of logistic regression.
+
+- Based on Eigen
+- Support L2 regulation
+- Support save/load weights
+
+###Dependency
+
+- Eigen
+
+
+###Usage
+```
+    //data prepare,10 samples
+	MatrixXd X(10,2);
+	X<<1.0,0.8,2.0,1.7,3.0,2.5,4.0,3.6,5.0,4.9,
+	   1.0,1.2,2.0,2.5,3.0,3.4,4.0,4.5,5.0,6.0;
+	VectorXi y(10);
+	y<<0,0,0,0,0,1,1,1,1,1;
+
+	//train and save the weights
+	LR clf1 = LR(200,0.01,0.05,0.01);  //max_iter=200,alpha=0.01(learning rate),l2_lambda=0.05,tolerance=0.01
+	clf1.fit(X,y);
+	cout<<"weights:\n"<<clf1.getW()<<endl; 
+	clf1.saveWeights("test.weights");
+
+	//load the weights and predict
+	LR clf2 = LR();
+	clf2.loadWeights("test.weights");
+	cout<<"Predict:\n"<<clf2.predict(X)<<endl;
+
+```
+
+###DirTree
+
+```
+.
+|-- common_functions.h
+|-- common_functions.cc
+|-- lr.h
+|-- lr.cc
+|-- main.cc
+|-- makefile
+|-- weights         [direction where save the weights]
+|  `-- test.weights
+|-- eigen_tutorial  [show the basic usage of Eigen]
+   `-- eigen_usage.cc
+
+
+```
+
+
diff --git a/logistic regression/use_cpp_and_eigen/common_functions.cc b/logistic regression/use_cpp_and_eigen/common_functions.cc
new file mode 100644
index 0000000..dd0716f
--- /dev/null
+++ b/logistic regression/use_cpp_and_eigen/common_functions.cc	
@@ -0,0 +1,18 @@
+#include <cmath>
+#include "common_functions.h"
+
+
+double CommonFunctions::sigmod(double x){
+	return 1.0/(1.0+exp(-x));
+}
+
+
+double CommonFunctions::crossEntropyLoss(Eigen::VectorXi y,Eigen::VectorXd h){
+	Eigen::VectorXd y_d = y.cast<double>();
+	int n = y_d.size();
+	double loss;
+	for(int i=0;i<n;i++){
+		loss -= (y_d(i)*log2(h(i))+(1-y_d(i))*log2(1-h(i)));
+	}
+	return loss/n;
+}
\ No newline at end of file
diff --git a/logistic regression/use_cpp_and_eigen/common_functions.h b/logistic regression/use_cpp_and_eigen/common_functions.h
new file mode 100644
index 0000000..ca348d1
--- /dev/null
+++ b/logistic regression/use_cpp_and_eigen/common_functions.h	
@@ -0,0 +1,17 @@
+#ifndef __COMMON_FUNCTIONS_H__
+#define __COMMON_FUNCTIONS_H__
+
+#include <eigen3/Eigen/Dense>
+
+
+class CommonFunctions{
+public:
+	// sigmod function, depend on <cmath> library
+	static double sigmod(double x);
+	static double crossEntropyLoss(Eigen::VectorXi y,Eigen::VectorXd h);
+
+};
+
+
+
+#endif
\ No newline at end of file
diff --git a/logistic regression/use_cpp_and_eigen/eigen_tutorial/eigen_usage.cc b/logistic regression/use_cpp_and_eigen/eigen_tutorial/eigen_usage.cc
new file mode 100644
index 0000000..15f8d07
--- /dev/null
+++ b/logistic regression/use_cpp_and_eigen/eigen_tutorial/eigen_usage.cc	
@@ -0,0 +1,110 @@
+/*
+Created on 2015/09/14
+Author: wepon, http://2hwp.com
+Reference: http://eigen.tuxfamily.org/dox/group__TutorialMatrixArithmetic.html
+*/
+
+#include <iostream>
+#include <eigen3/Eigen/Dense>
+using namespace Eigen;
+int main()
+{
+
+  /* Matrix */
+  Matrix2d m;  //2*2,double
+  m(0,0) = 3;
+  m(1,0) = 2.5;
+  m(0,1) = -1;
+  m(1,1) = m(1,0) + m(0,1);
+  std::cout << "m:\n" << m << std::endl;
+
+
+  //MatrixXd m1 =  MatrixXd::Random(3,3);  //Dynamic,double
+  //MatrixXd m1 =  MatrixXd::Zero(3,3);
+  //MatrixXd m1 =  MatrixXd::Ones(3,3);
+  MatrixXd m1 =  MatrixXd::Identity(3,3);
+  std::cout << "m1:\n" << m1 << std::endl;
+
+  
+
+  MatrixXd m2(2,2);  //Dynamic,double
+  m2<<1,2,3,4;
+  std::cout << "m2:\n" << m2.size() << std::endl;  //size: 4
+
+  std::cout << "m2*m2:\n" << m2*m2 << std::endl;   //cross product
+
+  
+
+
+  int rows=5;  
+  int cols=5;  
+  MatrixXf m3(rows,cols);  
+  m3<<( Matrix3f()<<1,2,3,4,5,6,7,8,9 ).finished(),
+  MatrixXf::Zero(3,cols-3),MatrixXf::Zero(rows-3,3),
+  MatrixXf::Identity(rows-3,cols-3);  
+  std::cout << "m3=\n" << m3 << std::endl;  
+  std::cout << "m3.rows: " << m3.rows() << std::endl;  
+  std::cout << "m3.cols: " << m3.cols() << std::endl;
+
+  std::cout << "m3.transpose():\n" << m3.transpose() << std::endl;
+  std::cout << "m3.adjoint():\n" << m3.adjoint() << std::endl; 
+
+  Matrix2d m4 =  Matrix2d::Constant(3.0);
+  std::cout << "m4:\n" << m4 << std::endl;
+
+
+  
+
+
+  /* Vector */
+  Vector2f v;  //2,float
+  //Vector2d v;
+  //VectorXd v(2);
+  v(0) = 4.4;
+  v(1) = v(0) - 1;
+  std::cout << "v:\n" << v << std::endl;
+
+  Vector2i vv;
+  vv<<1,2;
+  //std::cout<< "v-vv:\n"<<v-vv<<std::endl; // error
+
+  Vector2f v1;  //2,float
+  v1 << 4.0,8.0;
+  std::cout << "v1:\n" << v1 << std::endl;
+
+  std::cout << "v.*v1:\n" << v.dot(v1) << std::endl;   //dot product
+
+  std::cout << "v1.norm():\n" << v1.norm() << std::endl;
+  std::cout << "v1.squaredNorm():\n" << v1.squaredNorm() << std::endl;
+
+  Matrix2f m5;
+  m5<<1.0,2.0,3.0,4.0;
+
+  MatrixXf m6(2,3);
+  m6<<1.0,2.0,3.0,4.0,5.0,6.0;
+  std::cout<< "m6:\n"<<m6<<std::endl;
+  std::cout<< "m6:\n"<<m6.row(0)<<std::endl;  //1 2 3 
+
+
+  
+
+
+  /* Array */
+  Array4i v2;
+  v2<<1,2,3,4;
+  std::cout << "v2:\n" << v2 << std::endl;
+
+  MatrixXd m8(2,3);
+  std::cout<< m8.rows() << " " << m8.cols() << std::endl; 
+
+
+
+  MatrixXd X(10,2);
+  X<<1.0,0.8,2.0,1.7,3.0,2.5,4.0,3.6,5.0,4.9,
+     1.0,1.2,2.0,2.5,3.0,3.4,4.0,4.5,5.0,6.0;
+  MatrixXd X_new(X.rows(),X.cols()+1);
+  X_new<<X,MatrixXd::Ones(X.rows(),1);
+  std::cout << "X:\n" << X_new <<  std::endl << X_new.rows() << " " << X_new.cols() <<  std::endl;
+
+
+}
diff --git a/logistic regression/use_cpp_and_eigen/lr.cc b/logistic regression/use_cpp_and_eigen/lr.cc
new file mode 100644
index 0000000..17d201c
--- /dev/null
+++ b/logistic regression/use_cpp_and_eigen/lr.cc	
@@ -0,0 +1,123 @@
+#include <iostream>
+#include <fstream>
+#include <sstream>
+#include <string>
+#include <vector>
+#include "lr.h"
+#include "common_functions.h"
+
+using namespace Eigen;
+
+LR::LR(int max_i,double alp,double l2_lambda,double tolerance){
+	lambda = l2_lambda; 
+	max_iter = max_i;
+	tol = tolerance;
+	alpha = alp;
+}
+
+LR::~LR(){}
+
+
+
+void LR::fit(MatrixXd X,VectorXi y){
+	//learn VectorXd W, consider reg,max_iter,tol.   
+	//TODO: check X,y
+
+	//VectorXd W = VectorXd::Random(X.cols()+1); wrong! u can not declare W again,otherwise it didn't represent the class member
+	W = VectorXd::Random(X.cols()+1);  //the last column of weight represent b
+	MatrixXd X_new(X.rows(),X.cols()+1);
+	X_new<<X,MatrixXd::Ones(X.rows(),1);  //last column is 1.0
+
+	for(int iter=0;iter<max_iter;iter++){
+		VectorXd y_pred = predict_prob(X);
+        VectorXd y_d = y.cast<double>();  //cast type first
+		VectorXd E = y_pred - y_d;
+
+		W = (1.0-lambda/y.size())*W - alpha*X_new.transpose()*E;  //W:= (1-lambda/n_samples)W-alpha*X^T*E
+		//reference : http://blog.csdn.net/pakko/article/details/37878837
+		
+		//when loss<tol, break
+		double loss = CommonFunctions::crossEntropyLoss(y,predict_prob(X));
+		if(loss<=tol) break;
+
+	}
+
+}
+
+
+VectorXd LR::predict_prob(MatrixXd X){
+	//predict the probability (of label 1) for given data X
+	MatrixXd X_new(X.rows(),X.cols()+1);
+	X_new<<X,MatrixXd::Ones(X.rows(),1);
+	int num_samples = X_new.rows();
+	VectorXd y_pred_prob = VectorXd::Zero(num_samples);
+	for(int num=0;num<num_samples;num++){
+		y_pred_prob(num) = CommonFunctions::sigmod(X_new.row(num).dot(W));
+	}
+
+	return y_pred_prob;
+}
+
+
+VectorXi LR::predict(MatrixXd X){
+	//predict the label for given data X
+	VectorXd y_pred_prob = predict_prob(X);
+	VectorXi y_pred(y_pred_prob.size());
+	for(int num=0;num<y_pred_prob.size();num++){
+		y_pred(num) = y_pred_prob(num)>0.5?1:0;
+	}
+	return y_pred;
+}
+
+
+Eigen::VectorXd LR::getW(){
+	return W;
+}
+
+void LR::saveWeights(std::string filename){
+	//save the model (save the weight ) into filename. 
+	std::ofstream ofile;
+	std::string path = "./weights/"+filename;
+	ofile.open(path.c_str());
+	if (!ofile.is_open()){
+		std::cerr<<"Can not open the file when call LR::saveParams"<<std::endl;
+		return;
+    }
+
+    //W write into the file
+	for(int i=0;i<W.size()-1;i++){
+		ofile<<W(i)<<" ";
+	}
+	ofile<<W(W.size()-1);
+	ofile.close();
+}
+
+
+void LR::loadWeights(std::string filename){
+	//load the model (load the weight ) from filename.
+	std::ifstream ifile;
+	std::string path = "./weights/"+filename;
+	ifile.open(path.c_str());
+	if (!ifile.is_open()){
+		std::cerr<<"Can not open the file when call LR::loadParams"<<std::endl;
+		return;
+    }
+
+    //read the weights into vector<double>
+	std::string line;
+	std::vector<double> weights;
+	getline(ifile,line);    //only one line
+	std::stringstream ss(line); 
+	double tmp;
+	while(!ss.eof()){
+		ss>>tmp;
+		weights.push_back(tmp);
+	}
+
+	//initialize VectorXd with std::vector
+	W = VectorXd::Map(weights.data(),weights.size());
+
+	ifile.close();
+}
+
+
diff --git a/logistic regression/use_cpp_and_eigen/lr.h b/logistic regression/use_cpp_and_eigen/lr.h
new file mode 100644
index 0000000..b22bd38
--- /dev/null
+++ b/logistic regression/use_cpp_and_eigen/lr.h	
@@ -0,0 +1,27 @@
+#ifndef __LR_H__
+#define __LR_H__
+
+#include <eigen3/Eigen/Dense>
+#include <string>
+
+class LR{
+public:
+	LR(int max_i=100,double alp=0.01,double l2_lambda=0.05,double tolerance=0.01); //the params name can't be the same as the class member?
+	~LR();
+	void fit(Eigen::MatrixXd X,Eigen::VectorXi y);
+	Eigen::VectorXd getW();
+	Eigen::VectorXd predict_prob(Eigen::MatrixXd X);
+	Eigen::VectorXi predict(Eigen::MatrixXd X);
+	void saveWeights(std::string filename);
+	void loadWeights(std::string filename);
+private:
+	Eigen::VectorXd W;
+	int max_iter;
+	double lambda;  //l2 regulization
+	double tol;  // error tolence
+	double alpha;
+};
+
+
+
+#endif
\ No newline at end of file
diff --git a/logistic regression/use_cpp_and_eigen/main.cc b/logistic regression/use_cpp_and_eigen/main.cc
new file mode 100644
index 0000000..591b2ba
--- /dev/null
+++ b/logistic regression/use_cpp_and_eigen/main.cc	
@@ -0,0 +1,29 @@
+#include <iostream>
+#include <eigen3/Eigen/Dense>
+#include "lr.h"
+
+using namespace std;
+using namespace Eigen;
+
+int main(){
+
+	//data prepare,10 samples
+	MatrixXd X(10,2);
+	X<<1.0,0.8,2.0,1.7,3.0,2.5,4.0,3.6,5.0,4.9,
+	   1.0,1.2,2.0,2.5,3.0,3.4,4.0,4.5,5.0,6.0;
+	VectorXi y(10);
+	y<<0,0,0,0,0,1,1,1,1,1;
+
+	//train and save the weights
+	LR clf1 = LR(200,0.01,0.05,0.01);  //max_iter=200,alpha=0.01(learning rate),l2_lambda=0.05,tolerance=0.01
+	clf1.fit(X,y);
+	cout<<"weights:\n"<<clf1.getW()<<endl; 
+	clf1.saveWeights("test.weights");
+
+	//load the weights and predict
+	LR clf2 = LR();
+	clf2.loadWeights("test.weights");
+	cout<<"Predict:\n"<<clf2.predict(X)<<endl;
+
+	return 0;
+}
\ No newline at end of file
diff --git a/logistic regression/use_cpp_and_eigen/makefile b/logistic regression/use_cpp_and_eigen/makefile
new file mode 100644
index 0000000..4659f10
--- /dev/null
+++ b/logistic regression/use_cpp_and_eigen/makefile	
@@ -0,0 +1,3 @@
+src=main.cc lr.cc common_functions.cc
+main:$(src)
+	g++ -o main $(src) 
diff --git a/logistic regression/use_cpp_and_eigen/weights/test.weights b/logistic regression/use_cpp_and_eigen/weights/test.weights
new file mode 100644
index 0000000..1b37557
--- /dev/null
+++ b/logistic regression/use_cpp_and_eigen/weights/test.weights	
@@ -0,0 +1 @@
+-0.938248 0.952499 -0.0994332
\ No newline at end of file