When returning a qvector, the contents of the qvector are lost.

IknowQT

QVector<QVector<double>> RegressionClass::PolyRegCoeff(QVector<QVector<double>> x, int M, bool varZero)
{
    int varStart = 0;
    if (varZero) { varStart = 1; }

    int rA  = x[0].count();
    int N   = x[0].count();
    QVector<QVector<double>> matSquaredX(N, QVector<double>(M+1-varStart));

    /* estimated polynomial regression coefficients 계산 */
    for (int i = 0; i < N; i++)
    {
        for (int j = varStart; j < M + 1; j++)
			matSquaredX[i][j - varStart] = pow(x[i][0], j);
    }

    return matSquaredX;
}

I have code like this. When I try to return matSquaredX, size is 0.
In the for statement, the size of matSquaredX was three.

KroMignon

@IknowQT said in When returning a qvector, the contents of the qvector are lost.:

QVector<QVector<double>>*   get_newX() { return m_newX; };
QVector<QVector<double>>*   get_newY() { return m_newY; };

Pa->get_newX()[i][0] = X[i][0];
Pa->get_newY()[i][0] = Y[i][0];

If I read right your code, Pa->get_newX() and Pa->get_newY() returns a pointer!

Should be:

(*Pa->get_newX())[i][0] = X[i][0];
(*Pa->get_newY())[i][0] = Y[i][0];

But looks ugly to me, I would work with references or add some more helper functions, like setX() / setY()

SGaist

Hi,

How did you determine that size ?
Did you check the value of matSquaredX before the return statement ?

IknowQT

@SGaist

my mistake. I solved it.
I have one more question.

QVector<QVector<double>>*   get_newX() { return m_newX; };
QVector<QVector<double>>*   get_newY() { return m_newY; };

Pa->get_newX()[i][0] = X[i][0];
Pa->get_newY()[i][0] = Y[i][0];

c2679 error occurs.
Is there a way to enter a value by substituting?
If you don't declare it as a pointer, your code will work normally.

jsulm

@IknowQT said in When returning a qvector, the contents of the qvector are lost.:

c2679

Can you please post the actual errror message?

Instead of returning a pointer to a member you can also return a reference.

IknowQT

@jsulm

error C2679 binary '=': no operator with type 'T' as right operand, or no conversion allowed. MatrixClassLibrary D:\ProgramSrc\POP\MatrixClassLibrary\MatrixClassLibrary.cpp 38

jsulm

@IknowQT What type are X and Y?

KroMignon

@IknowQT said in When returning a qvector, the contents of the qvector are lost.:

QVector<QVector<double>>*   get_newX() { return m_newX; };
QVector<QVector<double>>*   get_newY() { return m_newY; };

Pa->get_newX()[i][0] = X[i][0];
Pa->get_newY()[i][0] = Y[i][0];

If I read right your code, Pa->get_newX() and Pa->get_newY() returns a pointer!

Should be:

(*Pa->get_newX())[i][0] = X[i][0];
(*Pa->get_newY())[i][0] = Y[i][0];

But looks ugly to me, I would work with references or add some more helper functions, like setX() / setY()