// version 1.0.0 14Feb2018
// Notes: matrices are long vectors with row-major storage
//    The i,j element of an r x c matrix is 
//    the (i-1)*r + (j-1) element of the of the vector
//    under zero-base indexing
import com.stata.sfi.*;
public class MyMatrix {
    int        r, c, TotalSize ;
    double[]   mat ;

    public MyMatrix(int rows, int cols) {
        r         = rows ;
        c         = cols ;
        TotalSize = rows*cols ;
        mat       = new double[TotalSize] ;

        for(int i = 0; i<TotalSize; i++) {
            mat[i] = 0.0 ;
        }
    }

    void divideByScalar(double val) {
        int  i, j ;

        for(i=0; i<r; i++) {
            for(j=0; j<c; j++) {
                mat[i*r + j] /= val ;  
            }
        }
    }

// Copy matrix object values to Stata matrix smname
    int copyJavatoStataMatrix(String smname) {
        int      i, j; 
        int      rc_st ;
        double   val ;
        String   msg ;

// create new Stata matrix
        rc_st = Matrix.createMatrix(smname,r,c,0) ;
        if (rc_st>0) {
            SFIToolkit.errorln("cannot create Stata matrix " + smname) ;
            return(rc_st) ;
        }
        for(i=0; i<r; i++) {
            for(j=0; j<c; j++) {
                val = mat[i*r+j] ;
// Put values in new Stata matrix
                rc_st = Matrix.storeMatrixAt(smname, i, j, val) ;
                if(rc_st>0) {
                    msg =  "{err}cannot access Stata matrix " + smname ;
                    SFIToolkit.errorln(msg) ;
                    return(rc_st) ;
                }
            }
        }
        return(rc_st) ;
    }

    double getValue(int i, int j) {      
        return( mat[i*r+j]) ;
    }
// Store val into (i,j)th element 
    void storeValue(int i, int j, double val) {
        mat[i*r+j] = val ;
    }
// Increment (i,j)th element  by val
    void incrementByValue(int i, int j, double val) {
        mat[i*r+j] += val ;
    }

}