sklearn.decomposition.sparse_encode¶
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sklearn.decomposition.sparse_encode(X, dictionary, gram=None, cov=None, algorithm=’lasso_lars’, n_nonzero_coefs=None, alpha=None, copy_cov=True, init=None, max_iter=1000, n_jobs=1, check_input=True, verbose=0)[source]¶ Sparse coding
Each row of the result is the solution to a sparse coding problem. The goal is to find a sparse array code such that:
X ~= code * dictionary
Read more in the User Guide.
Parameters: X : array of shape (n_samples, n_features)
Data matrix
dictionary : array of shape (n_components, n_features)
The dictionary matrix against which to solve the sparse coding of the data. Some of the algorithms assume normalized rows for meaningful output.
gram : array, shape=(n_components, n_components)
Precomputed Gram matrix, dictionary * dictionary’
cov : array, shape=(n_components, n_samples)
Precomputed covariance, dictionary’ * X
algorithm : {‘lasso_lars’, ‘lasso_cd’, ‘lars’, ‘omp’, ‘threshold’}
lars: uses the least angle regression method (linear_model.lars_path) lasso_lars: uses Lars to compute the Lasso solution lasso_cd: uses the coordinate descent method to compute the Lasso solution (linear_model.Lasso). lasso_lars will be faster if the estimated components are sparse. omp: uses orthogonal matching pursuit to estimate the sparse solution threshold: squashes to zero all coefficients less than alpha from the projection dictionary * X’
n_nonzero_coefs : int, 0.1 * n_features by default
Number of nonzero coefficients to target in each column of the solution. This is only used by algorithm=’lars’ and algorithm=’omp’ and is overridden by alpha in the omp case.
alpha : float, 1. by default
If algorithm=’lasso_lars’ or algorithm=’lasso_cd’, alpha is the penalty applied to the L1 norm. If algorithm=’threshold’, alpha is the absolute value of the threshold below which coefficients will be squashed to zero. If algorithm=’omp’, alpha is the tolerance parameter: the value of the reconstruction error targeted. In this case, it overrides n_nonzero_coefs.
copy_cov : boolean, optional
Whether to copy the precomputed covariance matrix; if False, it may be overwritten.
init : array of shape (n_samples, n_components)
Initialization value of the sparse codes. Only used if algorithm=’lasso_cd’.
max_iter : int, 1000 by default
Maximum number of iterations to perform if algorithm=’lasso_cd’.
n_jobs : int, optional
Number of parallel jobs to run.
check_input : boolean, optional
If False, the input arrays X and dictionary will not be checked.
verbose : int, optional
Controls the verbosity; the higher, the more messages. Defaults to 0.
Returns: code : array of shape (n_samples, n_components)
The sparse codes