get shape of eigen matrix

To get the shape of an Eigen matrix in C++, you can use the rows() and cols() member functions. Here is an explanation of each step:

  1. Include the necessary header: First, make sure you have included the Eigen library header in your C++ code. You can do so by adding the following line at the beginning of your code:

cpp #include <Eigen/Dense>

  1. Declare and initialize the matrix: Declare and initialize your Eigen matrix. For example, to create a 3x4 matrix of floating-point numbers, you can use the following code:

cpp Eigen::MatrixXf matrix(3, 4);

Here, Eigen::MatrixXf is the type of the matrix, and matrix is the name of the variable representing the matrix.

  1. Get the shape: To get the shape of the matrix, you can use the rows() and cols() member functions. These functions return the number of rows and columns of the matrix, respectively. Here is an example:

cpp int numRows = matrix.rows(); int numCols = matrix.cols();

The variables numRows and numCols will store the number of rows and columns of the matrix, respectively.

  1. Use the shape: You can now use the obtained values to perform further operations or print them. For example, you can print the shape of the matrix using the following code:

cpp std::cout << "Number of rows: " << numRows << std::endl; std::cout << "Number of columns: " << numCols << std::endl;

This code will output the number of rows and columns of the matrix.

That's it! You have successfully obtained the shape of an Eigen matrix in C++. Remember to include the necessary header, declare and initialize the matrix, get the shape using the rows() and cols() member functions, and use the obtained values as desired.