CODEWITHSUNDEEP
c++-cli
yalcin
yalcin

Reputation: 541

Defining a matrix as an array of arrays and computation its inverse matrix in C++

Unfortunately I haven't much experience in C++ and I'm trying to progress myself in C++.

Firstly,I defined array of arrays so that I formed an 3x3 matrix:

array< array< double >^ >^ input = gcnew array< array< double >^ >(3);

for (j=0;j<input->Length;j++){
    input[j]=gcnew array<double>(3);

Then I assigned matrix elements to input array of arrays:

 int value=1;
for(y=0;y<(3);y++){
  for(x=0;x<(3);x++)
 {input[y][x]=value;
  value=value+1;
  }
  }

Is there a C++ function that compute inverse matrix of this input array of arrays?

Could you help me please?

Best Regards...

Upvotes: 3

Views: 3329

Answers (5)

parth_sh
parth_sh

Reputation: 59

Code for inverse of matrix using Elementary row transformation in c++ 

#include<iostream>
#include<stdio.h>
#include<conio.h>
using
namespace std;

float a[4][4];float b[4][4]={{1,0,0,0},{0,1,0,0},{0,0,1,0},{0,0,0,1}};
int no = 4;

int check(int k) {
    float cont = 0, cont2 = 0;
    for (int i = k; i < no; i++) {
        if (a[i][k] == 1) {
            for (int j = 0; j < no; j++) {
                cont = a[i][j];
                cont2 = b[i][j];
                a[i][j] = a[k][j];
                b[i][j] = b[k][j];
                a[k][j] = cont;
                b[k][j] = cont2;
            }
        } else if (a[i][k] == 0) {
            for (int j = 0; j < no; j++) {
                cont = a[i][j];
                cont2 = b[i][j];
                a[i][j] = a[no - 1][j];
                b[i][j] = b[no - 1][j];
                a[no - 1][j] = cont;
                b[no - 1][j] = cont2;
            }
        }
    }
    return 0;
}

int divi(int k) {
    float particular = a[k][k];
    for (int i = 0; i < no; i++) {
        a[k][i] = a[k][i] / particular;
        b[k][i] = b[k][i] / particular;
        if (a[k][i] == (-0)) {
            a[k][i] = 0;
        }
        if (b[k][i] == (-0)) {
            b[k][i] = 0;
        }
    }
    return 0;
}

int sub1(int k) {
    float particular;
    for (int j = k + 1; j < no; j++) {
        particular = a[j][k];
        for (int i = 0; i < no; i++) {
            a[j][i] = a[j][i] - (particular * a[k][i]);
            b[j][i] = b[j][i] - (particular * b[k][i]);
            if (a[j][i] == (-0)) {
                a[j][i] = 0;
            }
            if (b[j][i] == (-0)) {
                b[j][i] = 0;
            }
        }
    }
    return 0;
}

int sub2(int k) {
    float particular;
    for (int j = k - 1; j >= 0; j--) {
        particular = a[j][k];
        for (int i = no - 1; i >= 0; i--) {
            a[j][i] = a[j][i] - (particular * a[k][i]);
            b[j][i] = b[j][i] - (particular * b[k][i]);
            if (a[j][i] == (-0)) {
                a[j][i] = 0;
            }
            if (b[j][i] == (-0)) {
                b[j][i] = 0;
            }
        }
    }
    return 0;
}

int disp(){
 cout<<endl;
             for(int x=0;x<no;x++){
             for(int y=0;y<no;y++){
                   if(a[x][y]==(-0)){a[x][y]=0;}
                   if(b[x][y]==(-0)){b[x][y]=0;}
                   printf("%0.1f|||%0.1f     ",a[x][y],b[x][y]);
             }
             cout<<endl;}
}

int main()
{
    for(int i=0;i<no;i++){
          for(int j=0;j<no;j++){cout<<"Enter a["<<i<<"]["<<j<<"]";cin>>a[i}[j];}
          }
    for(int i=0;i<no;i++){
            for(int j=0;j<no;j++){cout<<a[i][j]<<" ";}
    cout<<endl;
          }

    for(int i=0;i<no;i++){
        check(i);
            disp();
        divi(i);
            disp();
        sub1(i);
            disp();
    }
    for(int i=no-1;i>=0;i--){
     sub2(i);
     disp();
     cout<<endl;
     }
     getch();
     getch();
     getch();
 return 0;}

 }

Upvotes: 0

Pratik Deoghare
Pratik Deoghare

Reputation: 37222

There is not built in C++ function to do matrix inversion (or for any other matrix calculations).

There are lots of methods for matrix inversion mentioned HERE.

If you want efficiency and ease of implementation then Guassian Elimination is probably the best.

Upvotes: 0

grigy
grigy

Reputation: 6836

Look at Simple 3x3 matrix inverse code (C++).

Upvotes: 2

andreas buykx
andreas buykx

Reputation: 12960

Wikipedia has a list of numerical libraries in various programming languages. If the functions that you are looking for are not available you could also consider writing a wrapper function around an available Fortran or C or C++ implementation.

Upvotes: 0

Drakosha
Drakosha

Reputation: 12165

There are no functions in C++ to make matrix operations, you'll need to find some library to do it or implement your own.

Note that for fixed size arrays, you can use regular C/C++ arrays, like this one:

double arr[3][3];

Upvotes: 0

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