How to modify a method in runtime in c++?

I got here trying to transpose a matrix in O(1). So right now I have something like this:

#include <vector>

template <class T>
class Matrix {  //intended for math matrix
public:
    Matrix(int Rows, int Cols){matrix = vector<vector<T> >(Rows, vector<T>(Cols,0)); transpose = false; cols = Cols; rows = Rows;}
    Matrix(const Matrix<T> &M){matrix = M.matrix; transpose = M.transpose; cols = M.cols; rows = M.rows;}
    ~Matrix(){}

    void t(){
        transpose = !transpose; 
        swap(cols,rows);
    }

    T& operator()(int row, int col){
        if(transpose) 
            return matrix[col][row]; 
        else 
            return matrix[row][col];
    }

private:
    vector<vector<T> > matrix;
    bool transpose;
    int cols;
    int rows;
};

In that code I have what I want: t() is O(1) and operator() is also O(1). But operator() is used a lot and I want to take away the if.
So, to improve performance I want to have something like this:

#include <vector>

template <class T>
class Matrix {  //intended for math matrix
public:
    Matrix(int Rows, int Cols){matrix = vector<vector<T> >(Rows, vector<T>(Cols,0)); transpose = false; cols = Cols; rows = Rows;}
    Matrix(const Matrix<T> &M){matrix = M.matrix; transpose = M.transpose; cols = M.cols; rows = M.rows;}
    ~Matrix(){}

    T& originalShape(int row, int col){return matrix[row][col];}
    T& transposedMatrix(int row, int col){return matrix[col][row];}
    void t(){
        transpose = !transpose;
        swap(cols,rows);

        if(transpose)
            &operator() = &transposedMatrix;
        else
            &operator() = &originalShape;
    }
    T& operator()(int row, int col){return matrix[row][col];}

private:
    vector<vector<T> > matrix;
    bool transpose;
    int cols;
    int rows;
};

Of course, that doesn't work. And I didn't find anything useful for this case.

Is there anything I can do to improve this?