Creating a matrix? - c++

Question

I am trying to create a rotation matrix using Eigen::Matrix3d, but can't seem to do it accurately..
void rot(double x,double y,double z)
{
Eigen::Matrix3d x_r ((double)1,(double)0,(double)0,
(double)0,cos(x),-sin(x),
(double)0,sin(x),cos(x));
Eigen::Matrix3d y_r (cos(y),(double)0,sin(y),
(double)0,(double)1,(double)0,
-sin(y),(double)0,cos(y));
Eigen::Matrix3d z_r (cos(z),-sin(z),(double)0,
sin(z),cos(z),(double)0,
(double)0,(double)0,(double)1) ;
Eigen::Matrix3d rot = z_r*y_r*x_r;
}
I can't crate x_r,y_r,z_r for some weird reason?.. Could someone elaborate what i am doing wrong?
Error message i am receiving is:
error: no matching function for call to 'Eigen::Matrix<double, 3, 3>::Matrix(double, double, double, double, double, double, double, double, double)'
First i thought i was because i was using a combination of double and intwhich is why i typecasted it in the first place..

Answer 1

Try with
Eigen::Matrix3d x_r;
Eigen::Matrix3d y_r;
Eigen::Matrix3d z_r;
x_r << 1.0, 0.0, 0.0,
0.0, cos(x), -sin(x),
0.0 ,sin(x), cos(x);
y_r << cos(y), 0.0, sin(y),
0.0, 1.0, 0.0,
-sin(y), 0.0, cos(y);
z_r << cos(z), -sin(z), 0.0,
sin(z), cos(z), 0.0,
0.0, 0.0, 1.0;
Eigen::Matrix3d rot = z_r*y_r*x_r;
Seems that there isn't the constructor of Eigen::Matrix3d you're trying to use: a constructor that initializes the values directly.

Answer 2

In your example you try to construct the matrix by passing the matrix entries in the constructor. But the constructor does not take the matrix entries as arguments, even if it is a fixed (matrix) size type like Eigen::Matrix3d. You can set the matrix entries with the overloaded operator() after the matrix object is constructed, e.g.:
Eigen::Matrix3d M;
M( 0,0 ) = 1.0;
M( 0,1 ) = 0.0;
M( 0,2 ) = 0.0;
M( 1,0 ) = 0.0;
M( 1,1 ) = cos( x );
M( 1,2 ) = -sin( x );
M( 1,0 ) = 0.0;
M( 1,1 ) = sin( x );
M( 1,2 ) = cos( x );