#include<stdio.h>
#include<math.h>

double xx[100][100];

void main()
{
    double x[1000][100],y[1000],b[100],xy[100];
    int i,j,k,m,n;
    void inverse(int k);

/*
   input: x[1000][100],y[1000],n,k
   output: b[100]
*/

    n=5;
    k=2;

    FILE *fn;
    fn=fopen("data.txt","r");
    for(m=1;m<=n;++m){
      fscanf(fn,"%lf",&y[m]);
      for(j=1;j<=k;++j) fscanf(fn,"%lf",&x[m][j]);
      if(m != n) fscanf(fn,"\n");
    }
    fclose(fn);

    for(i=1;i<=k;++i){
      xy[i]=0.0;
      for(m=1;m<=n;++m) xy[i]+=x[m][i]*y[m];
    }
    for(i=1;i<=k;++i){
      for(j=1;j<=k;++j){
        xx[i][j]=0.0;
        for(m=1;m<=n;++m) xx[i][j]+=x[m][i]*x[m][j];
      }
    }

    inverse(k);
    for(i=1;i<=k;++i){
      b[i]=0.0;
      for(j=1;j<=k;++j) b[i]+=xx[i][j]*xy[j];
    }

    printf("Regression Coeff.:\n");
    for(i=1;i<=k;++i) printf("%15.7lf",b[i]);

    fn=fopen("res.txt","w");
    fprintf(fn,"Regression Coeff.:\n");
    for(i=1;i<=k;++i) fprintf(fn,"%15.7lf",b[i]);
    fclose(fn);

}
/* ---------------------------------------------------------- */
void inverse(int k)
{
   double a1,a2;
   int    i,j,m;

   for(i=1;i<=k;i++){
      a1=xx[i][i];
      xx[i][i]=1.0;
      for(j=1;j<=k;j++) xx[i][j]=xx[i][j]/a1;
      for(m=1;m<=k;m++){
         if(m != i){
            a2=xx[m][i];
            xx[m][i]=0.0;
            for(j=1;j<=k;j++) xx[m][j]-=a2*xx[i][j];
         }
      }
   }
}