# sklearn.decomposition.non_negative_factorization¶

sklearn.decomposition.non_negative_factorization(X, W=None, H=None, n_components=None, init=’warn’, update_H=True, solver=’cd’, beta_loss=’frobenius’, tol=0.0001, max_iter=200, alpha=0.0, l1_ratio=0.0, regularization=None, random_state=None, verbose=0, shuffle=False)[source]

Compute Non-negative Matrix Factorization (NMF)

Find two non-negative matrices (W, H) whose product approximates the non- negative matrix X. This factorization can be used for example for dimensionality reduction, source separation or topic extraction.

The objective function is:

0.5 * ||X - WH||_Fro^2
+ alpha * l1_ratio * ||vec(W)||_1
+ alpha * l1_ratio * ||vec(H)||_1
+ 0.5 * alpha * (1 - l1_ratio) * ||W||_Fro^2
+ 0.5 * alpha * (1 - l1_ratio) * ||H||_Fro^2


Where:

||A||_Fro^2 = \sum_{i,j} A_{ij}^2 (Frobenius norm)
||vec(A)||_1 = \sum_{i,j} abs(A_{ij}) (Elementwise L1 norm)


For multiplicative-update (‘mu’) solver, the Frobenius norm (0.5 * ||X - WH||_Fro^2) can be changed into another beta-divergence loss, by changing the beta_loss parameter.

The objective function is minimized with an alternating minimization of W and H. If H is given and update_H=False, it solves for W only.

Parameters: X : array-like, shape (n_samples, n_features) Constant matrix. W : array-like, shape (n_samples, n_components) If init=’custom’, it is used as initial guess for the solution. H : array-like, shape (n_components, n_features) If init=’custom’, it is used as initial guess for the solution. If update_H=False, it is used as a constant, to solve for W only. n_components : integer Number of components, if n_components is not set all features are kept. init : None | ‘random’ | ‘nndsvd’ | ‘nndsvda’ | ‘nndsvdar’ | ‘custom’ Method used to initialize the procedure. Default: ‘random’. The default value will change from ‘random’ to None in version 0.23 to make it consistent with decomposition.NMF. Valid options: None: ‘nndsvd’ if n_components < n_features, otherwise ‘random’. ‘random’: non-negative random matrices, scaled with: sqrt(X.mean() / n_components) ‘nndsvd’: Nonnegative Double Singular Value Decomposition (NNDSVD) initialization (better for sparseness) ‘nndsvda’: NNDSVD with zeros filled with the average of X (better when sparsity is not desired) ‘nndsvdar’: NNDSVD with zeros filled with small random values (generally faster, less accurate alternative to NNDSVDa for when sparsity is not desired) ‘custom’: use custom matrices W and H update_H : boolean, default: True Set to True, both W and H will be estimated from initial guesses. Set to False, only W will be estimated. solver : ‘cd’ | ‘mu’ Numerical solver to use: ‘cd’ is a Coordinate Descent solver that uses Fast Hierarchical Alternating Least Squares (Fast HALS). ‘mu’ is a Multiplicative Update solver. New in version 0.17: Coordinate Descent solver. New in version 0.19: Multiplicative Update solver. beta_loss : float or string, default ‘frobenius’ String must be in {‘frobenius’, ‘kullback-leibler’, ‘itakura-saito’}. Beta divergence to be minimized, measuring the distance between X and the dot product WH. Note that values different from ‘frobenius’ (or 2) and ‘kullback-leibler’ (or 1) lead to significantly slower fits. Note that for beta_loss <= 0 (or ‘itakura-saito’), the input matrix X cannot contain zeros. Used only in ‘mu’ solver. New in version 0.19. tol : float, default: 1e-4 Tolerance of the stopping condition. max_iter : integer, default: 200 Maximum number of iterations before timing out. alpha : double, default: 0. Constant that multiplies the regularization terms. l1_ratio : double, default: 0. The regularization mixing parameter, with 0 <= l1_ratio <= 1. For l1_ratio = 0 the penalty is an elementwise L2 penalty (aka Frobenius Norm). For l1_ratio = 1 it is an elementwise L1 penalty. For 0 < l1_ratio < 1, the penalty is a combination of L1 and L2. regularization : ‘both’ | ‘components’ | ‘transformation’ | None Select whether the regularization affects the components (H), the transformation (W), both or none of them. random_state : int, RandomState instance or None, optional, default: None If int, random_state is the seed used by the random number generator; If RandomState instance, random_state is the random number generator; If None, the random number generator is the RandomState instance used by np.random. verbose : integer, default: 0 The verbosity level. shuffle : boolean, default: False If true, randomize the order of coordinates in the CD solver. W : array-like, shape (n_samples, n_components) Solution to the non-negative least squares problem. H : array-like, shape (n_components, n_features) Solution to the non-negative least squares problem. n_iter : int Actual number of iterations.

References

Cichocki, Andrzej, and P. H. A. N. Anh-Huy. “Fast local algorithms for large scale nonnegative matrix and tensor factorizations.” IEICE transactions on fundamentals of electronics, communications and computer sciences 92.3: 708-721, 2009.

Fevotte, C., & Idier, J. (2011). Algorithms for nonnegative matrix factorization with the beta-divergence. Neural Computation, 23(9).

Examples

>>> import numpy as np
>>> X = np.array([[1,1], [2, 1], [3, 1.2], [4, 1], [5, 0.8], [6, 1]])
>>> from sklearn.decomposition import non_negative_factorization
>>> W, H, n_iter = non_negative_factorization(X, n_components=2,
... init='random', random_state=0)