十年磨一剑

As shown above, static methods as Zero() and Constant() can be used to initialize variables at the time of declaration or at the right-hand side of an assignment operator. You can think of these metho

Matrix-matrix multiplication is again done with operator*. Since vectors are a special case of matrices, they are implicitly handled there too, so matrix-vector product is really just a special case o

Matrix4f mymatrix; really amounts to just doingfloat mymatrix[16]; so this really has zero runtime cost. By contrast, the array of a dynamic-size matrix is always allocated on the he

The transpose , conjugate , and adjoint (i.e., conjugate transpose)  of a matrix or vector  are obtained by the member functions transpose(), conjugate(), and adjoint(), respectively.E

Eigen also provides some reduction operations to reduce a given matrix or vector to a single value such as the sum (computed by sum()), product (prod()), or the maximum (maxCoeff()) and minimum

First of all, of course you can multiply an array by a scalar, this works in the same way as matrices. Where arrays are fundamentally different from matrices, is when you multiply two together. Matric

1. download eigen from the link : http://eigen.tuxfamily.org/index.php?title=Main_Page2.extract and copy to a location you wantsudo cp -avr /home/tjiang/Downloads/eigen-eigen-b30b87236a1

the reason is missing EIGEN3_INCLUDE_DIRthen we need to define it in cmakelist.txt fileadd a line like this in this file:Set(EIGEN3_INCLUDE_DIR "/usr/local/include/eigen-eigen-b30b87236a1b")

In many papers(such as [1], [2]), we need to solve the polar decomposition of a matrix which decompose a matrix A into a rotation matrix R and a symmetric matrix S, s.t. A = RSHere, we will be u

The (Euclidean a.k.a. ) squared norm of a vector can be obtained squaredNorm() . It is equal to the dot product of the vector by itself, and equivalently to the sum of squared absolute values of its

When should you use objects of the Matrix class and when should you use objects of the Array class? You cannot applyMatrix operations on arrays, or Array operations on matrices. Thus, if you n

The Array class defines other coefficient-wise operations besides the addition, subtraction and multiplication operators described above. For example, the .abs() method takes the absolute value of

Eigen offers a comma initializer syntax which allows the user to easily set all the coefficients of a matrix, vector or array. Simply list the coefficients, starting at the top-left corner and movin

The most general block operation in Eigen is called .block() . There are two versions, whose syntax is as follows:Block operationVersion constructing a dynamic-size block expressio

In Eigen, a reduction is a function taking a matrix or array, and returning a single scalar value. One of the most used reductions is .sum() , returning the sum of all the coefficients inside a gi

AliasingDense matrix and array manipulationIn Eigen, aliasing refers to assignment statement in which the same matrix (or array or vector) appears on the left and on the right of the ass

#include #include using namespace Eigen;using namespace std;int main(){ MatrixXd m = MatrixXd::Random(3, 3); m = (m + MatrixXd::Constant(3, 3, 1.2)) * 50; cout << "m =" << endl << m << endl;

There are two different storage orders for matrices and two-dimensional arrays: column-major and row-major. This page explains these storage orders and how to specify which one should be used.Colu

The resize() method is a no-operation if the actual matrix size doesn't change; otherwise it is destructive: the values of the coefficients may change. If you want a conservative variant of resize()

Eigen defines the following Matrix typedefs:MatrixNt for Matrix. For example, MatrixXi for Matrix.VectorNt for Matrix. For example, Vector2f for Matrix.RowVectorNt for Matrix. For example, RowVect

The Eigen/Dense header file defines all member functions for the MatrixXd type and related types

Eigen/src/Core/util/Macros.h