Added growth method for solving diffrential equations, added dy, dx, gradient magnitude and orientation of image calculators

MLPP/Convolutions/Convolutions.cpp

@@ -245,6 +245,82 @@ namespace MLPP{
         return filter;
     }
 
+    /* 
+    Indeed a filter could have been used for this purpose, but I decided that it would've just 
+    been easier to carry out the calculation explicitly, mainly because it is more informative, 
+    and also because my convolution algorithm is only built for filters with equally sized 
+    heights and widths.
+    */
+    std::vector<std::vector<double>> Convolutions::dx(std::vector<std::vector<double>> input){
+        std::vector<std::vector<double>> deriv; // We assume a gray scale image. 
+        deriv.resize(input.size());
+        for(int i = 0; i < deriv.size(); i++){
+            deriv[i].resize(input[i].size());
+        }
+
+        for(int i = 0; i < input.size(); i++){
+            for(int j = 0; j < input[i].size(); j++){
+                if(j != 0 && j != input.size() - 1){
+                    deriv[i][j] = input[i][j + 1] - input[i][j - 1];
+                }
+                else if(j == 0){
+                    deriv[i][j] = input[i][j + 1] - 0; // Implicit zero-padding
+                }
+                else{
+                    deriv[i][j] = 0 - input[i][j - 1]; // Implicit zero-padding
+                }
+            }
+        }
+        return deriv;
+    }
+
+    std::vector<std::vector<double>> Convolutions::dy(std::vector<std::vector<double>> input){
+        std::vector<std::vector<double>> deriv; 
+        deriv.resize(input.size());
+        for(int i = 0; i < deriv.size(); i++){
+            deriv[i].resize(input[i].size());
+        }
+
+        for(int i = 0; i < input.size(); i++){
+            for(int j = 0; j < input[i].size(); j++){
+                if(i != 0 && i != input.size() - 1){
+                    deriv[i][j] = input[i - 1][j] - input[i + 1][j];
+                }
+                else if(i == 0){
+                    deriv[i][j] = 0 - input[i + 1][j]; // Implicit zero-padding
+                }
+                else{
+                    deriv[i][j] = input[i - 1][j] - 0; // Implicit zero-padding
+                }
+            }
+        }
+        return deriv;
+    }
+
+    std::vector<std::vector<double>> Convolutions::gradMagnitude(std::vector<std::vector<double>> input){
+        LinAlg alg;
+        std::vector<std::vector<double>> xDeriv_2 = alg.hadamard_product(dx(input), dx(input));
+        std::vector<std::vector<double>> yDeriv_2 = alg.hadamard_product(dy(input), dy(input));
+        return alg.sqrt(alg.addition(xDeriv_2, yDeriv_2));
+    }
+
+    std::vector<std::vector<double>> Convolutions::gradOrientation(std::vector<std::vector<double>> input){
+        std::vector<std::vector<double>> deriv; 
+        deriv.resize(input.size());
+        for(int i = 0; i < deriv.size(); i++){
+            deriv[i].resize(input[i].size());
+        }
+
+        std::vector<std::vector<double>> xDeriv = dx(input);
+        std::vector<std::vector<double>> yDeriv = dy(input);
+        for(int i = 0; i < deriv.size(); i++){
+            for(int j = 0; j < deriv[i].size(); j++){
+                deriv[i][j] = std::atan2(yDeriv[i][j], xDeriv[i][j]);
+            }
+        }
+        return deriv;
+    }
+
     std::vector<std::vector<double>> Convolutions::getPrewittHorizontal(){
         return prewittHorizontal;
     }

MLPP/Convolutions/Convolutions.hpp

@@ -17,6 +17,12 @@ namespace MLPP{
             double gaussian2D(double x, double y, double std);
             std::vector<std::vector<double>> gaussianFilter2D(int size, double std);
 
+            std::vector<std::vector<double>> dx(std::vector<std::vector<double>> input);
+            std::vector<std::vector<double>> dy(std::vector<std::vector<double>> input);
+
+            std::vector<std::vector<double>> gradMagnitude(std::vector<std::vector<double>> input);
+            std::vector<std::vector<double>> gradOrientation(std::vector<std::vector<double>> input);
+
             std::vector<std::vector<double>> getPrewittHorizontal();
             std::vector<std::vector<double>> getPrewittVertical();
             std::vector<std::vector<double>> getSobelHorizontal();

MLPP/NumericalAnalysis/NumericalAnalysis.cpp

@@ -163,6 +163,22 @@ namespace MLPP{
         }
         return y;
     }
+
+    double NumericalAnalysis::growthMethod(double C, double k, double t){
+        /* 
+        dP/dt = kP
+        dP/P = kdt
+        integral(1/P)dP = integral(k) dt
+        ln|P| = kt + C_initial
+        |P| = e^(kt + C_initial)
+        |P| = e^(C_initial) * e^(kt)
+        P = +/- e^(C_initial) * e^(kt)
+        P = C * e^(kt)
+        */
+
+        // auto growthFunction = [&C, &k](double t) { return C * exp(k * t); };
+        return C * exp(k * t);
+    }
     
     std::vector<double> NumericalAnalysis::jacobian(double(*function)(std::vector<double>), std::vector<double> x){
         std::vector<double> jacobian; 

MLPP/NumericalAnalysis/NumericalAnalysis.hpp

@@ -35,6 +35,8 @@ namespace MLPP{
             double eulerianMethod(double(*derivative)(double), std::vector<double> q_0, double p, double h); // Euler's method for solving diffrential equations. 
             double eulerianMethod(double(*derivative)(std::vector<double>), std::vector<double> q_0, double p, double h); // Euler's method for solving diffrential equations. 
 
+            double growthMethod(double C, double k, double t); // General growth-based diffrential equations can be solved by seperation of variables.
+
             std::vector<double> jacobian(double(*function)(std::vector<double>), std::vector<double> x); // Indeed, for functions with scalar outputs the Jacobians will be vectors.
             std::vector<std::vector<double>> hessian(double(*function)(std::vector<double>), std::vector<double> x);
             std::vector<std::vector<std::vector<double>>> thirdOrderTensor(double(*function)(std::vector<double>), std::vector<double> x);

main.cpp

@@ -542,16 +542,16 @@ int main() {
     //  alg.printMatrix(R); 
 
     // // Checking positive-definiteness checker. For Cholesky Decomp. 
-    // std::vector<std::vector<double>> A = 
-    // {
-    //     {1,-1,-1,-1},                        
-    //     {-1,2,2,2},
-    //     {-1,2,3,1},
-    //     {-1,2,1,4}
-    // };
+    std::vector<std::vector<double>> A = 
+    {
+        {1,-1,-1,-1},                        
+        {-1,2,2,2},
+        {-1,2,3,1},
+        {-1,2,1,4}
+    };
 
     // std::cout << std::boolalpha << alg.positiveDefiniteChecker(A) << std::endl;
-    // auto [L, Lt] = alg.chol(A); // WORKS !!!!
+    // auto [L, Lt] = alg.chol(A); // works.
     // alg.printMatrix(L);
     // alg.printMatrix(Lt);
 
@@ -597,9 +597,14 @@ int main() {
 
     // std::cout << numAn.cubicApproximation(f_mv, {0, 0, 0}, {1, 1, 1}) << std::endl;
 
-    //std::cout << numAn.eulerianMethod(f_prime, {1, 1}, 1.5, 0.000001) << std::endl;
+    // std::cout << numAn.eulerianMethod(f_prime, {1, 1}, 1.5, 0.000001) << std::endl;
 
-    std::cout << numAn.eulerianMethod(f_prime_2var, {2, 3}, 2.5, 0.00000001) << std::endl;
+    // std::cout << numAn.eulerianMethod(f_prime_2var, {2, 3}, 2.5, 0.00000001) << std::endl;
+
+    // alg.printMatrix(conv.dx(A));
+    // alg.printMatrix(conv.dy(A));
+
+    alg.printMatrix(conv.gradOrientation(A));
 
     return 0;
 }