matrix - the value of the object is null once I get out of the function (Java) -

- 

import java.util.*;   public class algorithm {  public static class matrix{          private double[][] x; }  public static scanner scan = new scanner(system.in); private static string str;  public static void read_data(double[] radians, double[] l) {     l[0] = 0.0;     int i;     (i = 0; < 9; i++) {         str = scan.next();  //passem la primera columna         str = scan.next();  //agafem el valor del desplaçament         str = str.substring(0, str.length()-1); //traiem la coma         l[i+1] = double.parsedouble(str);          str = scan.next();  //passem la primera columna         str = scan.next();  //agafem el valor del desplaçament         if (i < 9) str = str.substring(0, str.length()-1);  //traiem la coma         radians[i] = math.toradians(double.parsedouble(str));     }     radians[i] = 0.0; }  public static void print_matrix(double[][] m) {     (int k = 0; k < 4; k++) {         system.out.print("\n");         (int j = 0; j < 4; j++) {             system.out.print(string.valueof(m[k][j]) + " , ");         }     } }  public static void print_jacobian(double[][] m) {     system.out.print("jacobian matrix =");     (int k = 0; k < 3; k++) {         system.out.print("\n");         (int j = 0; j < 9; j++) {             system.out.print(string.valueof(m[k][j]) + " , ");         }     } }  public static void init_matrix(double[][] m, int i, double[] radians, double[] l) {      m[0][3] = l[i];     m[0][0] = math.cos(radians[i]);     m[0][1] = -math.sin(radians[i]);     m[1][0] = math.sin(radians[i]);     m[1][1] = math.cos(radians[i]);      (int k = 0; k < 4; k++) {         (int j = 0; j < 4; j++) {             if (k == j && (m[k][j] == null)) m[k][j] = 1.0;             else if(m[k][j] == null) m[k][j] = 0.0;             //system.out.print(string.valueof(m[k][j]) + "\n");         }     } }  public static void init_ultima_matrix(double[][] m, int i, double[] l) {     m[0][3] = l[i];     (int k = 0; k < 4; k++) {         (int j = 0; j < 4; j++) {             if (k == j) m[k][j] = 1.0;             else if(m[k][j] == null) m[k][j] = 0.0;         }     } }  public static void init_derivada(double[][] m, int i, double[] radians) {     m[0][0] = -math.sin(radians[i]);     m[0][1] = -math.cos(radians[i]);     m[1][0] = math.cos(radians[i]);     m[1][1] = -math.sin(radians[i]);      (int k = 0; k < 4; k++) {         (int j = 0; j < 4; j++) {             if(m[k][j] == null) m[k][j] = 0.0;         }     } }  public static void init_ultima_derivada(double[][] m, int i) {     (int k = 0; k < 4; k++) {         (int j = 0; j < 4; j++) {             m[k][j] = 0.0;         }     } }  public static void fulfill_ts(matrix[] ts, double[] radians, double[] l) {     int i;     (i = 0; < 9; i++) {         ts[i].x = new double[4][4];         init_matrix(ts[i].x, i, radians, l);         //print_matrix(ts[i].x);     }     init_ultima_matrix(ts[i].x, i, l);  }  public static void fulfill_ds(matrix[] ds, double[] radians) {     int i;     (i = 0; < 9; i++) {         ds[i].x = new double[4][4];         init_derivada(ds[i].x, i, radians);     }     init_ultima_derivada(ds[i].x, i); }  private static double[][] product(double[][] a, double[][] b){       double suma = 0.0;       double result[][] = new double[4][4];       for(int = 0; < 4; i++){           for(int j = 0; j < 4; j++){               suma = 0.0;               for(int k = 0; k < 4; k++){                   suma += a[i][k] * b[k][j];               }               result[i][j] = suma;           }       }       return result;   }  private static void calc_t(matrix[] ts, double[][] t) {     t = ts[0].x;     (int j = 1; j < 10; j++) {         t = product(t, ts[j].x);     } }  private static void calc_jacobian(matrix[] ts, matrix[] ds, int i, double[][] jacobian) {     double[][] tmp;     if (i == 0) tmp = ds[0].x;     else tmp = ts[0].x;      (int j = 1; j < 10; j++) {         if (j == i) tmp = product(tmp, ds[j].x);         else tmp = product(tmp, ts[j].x);     }     jacobian[0][i] = tmp[0][3];     jacobian[1][i] = tmp[1][3];     jacobian[2][i] = tmp[0][0]; }    public static void main(string[] args) {     matrix[] ts = new matrix[10];     matrix[] ds = new matrix[10];      (int = 0; < 10; i++) {         ts[i] = new matrix();         ts[i].x = new double[4][4];         ds[i] = new matrix();          ds[i].x = new double[4][4];     }      double[] radians = new double[10];     double[] l = new double[10];     read_data(radians, l);     fulfill_ts(ts, radians, l);     fulfill_ds(ds, radians);     matrix t = new matrix();     t.x = new double[4][4];     system.out.print("\n ts matrix =");     (int q=0; q<10; ++q) print_matrix(ts[q].x);     calc_t(ts, t.x);     system.out.print("\n t matrix =");     print_matrix(t.x);     matrix jacobian = new matrix();     jacobian.x = new double[3][9];      (int j=0; j<9; j++)         calc_jacobian(ts, ds, j, jacobian.x);     print_jacobian(jacobian.x);     //la matriu jacobiana hauria d'estar acabada } }

hello here's code. problem in function "calc_t(matrix[] ts, double[][] t)", if print value of t before exit function, it's ok; if once i've gone out of function, says:

t matrix = null , null , null , null , null , null , null , null , null , null , null , null , null , null , null , null

can me?

thank much

this problem:

private static void calc_t(matrix[] ts, double[][] t) {     t = ts[0].x;     ... }

arguments in java passed by value. basically, you're ignoring original value of t, assigning new value it, , doing nothing - that's not going change caller. want like:

private static double[][] calc_t(matrix[] ts) {     double[] t = ts[0].x;     (int j = 1; j < 10; j++) {         t = product(t, ts[j].x);     }     return t; }

then call as:

t.x = calc_t(ts);

you should strongly consider using double[][] instead of double[][] unless need able represent nulls, , start following java naming conventions.


Comments

Post a Comment

Popular posts from this blog

c++ - OpenCV Error: Assertion failed <scn == 3 ::scn == 4> in unknown function, -

-
i read alot other solution still confused should mine... #include <opencv2/objdetect/objdetect.hpp> #include <opencv2/highgui/highgui.hpp> #include <opencv2/imgproc/imgproc.hpp> #include <iostream> #include <stdio.h> using namespace std; using namespace cv; int main(int argc, const char** argv) { //create cascade classifier object used face detection cascadeclassifier face_cascade; //use haarcascade_frontalface_alt.xml library face_cascade.load("haarcascade_frontalface_alt.xml"); //setup video capture device , link first capture device videocapture capturedevice; capturedevice.open(0); //setup image files used in capture process mat captureframe; mat grayscaleframe; //create window present results namedwindow("outputcapture", 1); //create loop capture , find faces while (true) { //capture new image frame capturedevice >> captureframe; ...
Read more

php - render data via PDO::FETCH_FUNC vs loop -

-
i've been using 2 methods render data. the first one: function name($id,$name){ return '<div id="'.$id.'">'.$name.'</div>'; } echo implode($pdo->query("select id,name user")->fetchall(pdo::fetch_func,'name')); the second one: $users = $pdo->query("select id,name user")->fetchall(pdo::fetch_obj); foreach($users $user){ echo name($user->id,$user->name); } i don't understand how pdo::fetch_func works. tried figure out. however, not well-documented. could please explain fetch mode? , also, 1 performs better? thank you. both methods wrong , have learn how use templates , how separate business logic presentation logic. $users = $pdo->query("select id,name user")->fetchall(pdo::fetch_obj); tpl::assign('users', $users); is code business logic part. then in template <?php foreach $users $row): ?> <div id="<?=$...
Read more

The canvas has been tainted by cross-origin data in chrome only -

-
uncaught securityerror: failed execute 'getimagedata' on 'canvasrenderingcontext2d': canvas has been tainted cross-origin data i getting above error in chrome. code(following) works fine in mozilla. have not corss domain issue. why above error in chrome? var wheel_canvas, wheel_context, can_w, can_h, wheel_grd; var large_radius = 160; var small_radius = 120; var wheel_canvas = document.getelementbyid('wheel_canvas'); var wheel_context = wheel_canvas.getcontext('2d'); var can_w = $(wheel_canvas).width(); var can_h = $(wheel_canvas).height(); var centerx = can_w / 2, centery = can_h / 2; var wheel_grd = null; test('#ff0000'); function test(hex) { $('#clrpicker').css({'left': 210, 'top': 210 }); inverted = hexbw(hex); $('#color_val_show').val(hex); current_color_hex_val_selected = hex; $('#color_val_show').css({'color':inverted,'background':hex}); fillgradient...
Read more