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The first principal eigenvector of the graph is also referred to merely as the principal eigenvector. The principal eigenvector is used to measure the centrality of its vertices. An example is Google's PageRank algorithm. The principal eigenvector of a modified adjacency matrix of the
In power iteration, for example, the eigenvector is actually computed before the eigenvalue (which is typically computed by the Rayleigh quotient of the eigenvector). [11] In the QR algorithm for a Hermitian matrix (or any normal matrix), the orthonormal eigenvectors are obtained as a product of the Q matrices from the steps in the algorithm. [11]
Given an n × n square matrix A of real or complex numbers, an eigenvalue λ and its associated generalized eigenvector v are a pair obeying the relation [1] =,where v is a nonzero n × 1 column vector, I is the n × n identity matrix, k is a positive integer, and both λ and v are allowed to be complex even when A is real.l When k = 1, the vector is called simply an eigenvector, and the pair ...
Now, fix a basis B of V over K and suppose M ∈ Mat K (V) is a matrix. Define the linear map T : V → V pointwise by Tx = Mx, where on the right-hand side x is interpreted as a column vector and M acts on x by matrix multiplication. We now say that x ∈ V is an eigenvector of M if x is an eigenvector of T.
Principal component analysis (PCA) is a linear dimensionality reduction technique with applications in exploratory data analysis, visualization and data preprocessing.. The data is linearly transformed onto a new coordinate system such that the directions (principal components) capturing the largest variation in the data can be easily identified.
Then an eigenvector and the corresponding eigenvalue must satisfy the equation =, or, equivalently (since =), = where is the identity matrix, and (although the zero vector satisfies this equation for every , it is not considered an eigenvector). It follows that the matrix () must be singular, and its determinant = must be zero.
The number is known as the (nonlinear) eigenvalue, the vector as the (nonlinear) eigenvector, and (,) as the eigenpair. The matrix M ( λ ) {\displaystyle M(\lambda )} is singular at an eigenvalue λ {\displaystyle \lambda } .
The vector = (,,, …,) is an eigenvector of this matrix, where the eigenvalue is a root of (). Setting the initial values of the sequence equal to this vector produces a geometric sequence a k = λ k {\displaystyle a_{k}=\lambda ^{k}} which satisfies the recurrence.