Source Code for Module parsimony.datasets.simulate.beta

 1  # -*- coding: utf-8 -*- 
 2  """ 
 3  Created on Thu Sep 26 10:12:56 2013 
 4   
 5  Copyright (c) 2013-2014, CEA/DSV/I2BM/Neurospin. All rights reserved. 
 6   
 7  @author:  Tommy Löfstedt 
 8  @email:   tommy.loefstedt@cea.fr 
 9  @license: BSD 3-clause. 
10  """ 
11  import numpy as np 
12  import utils 
13   
14  __all__ = ['random'] 
15   
16   
17 -def random(shape, density=1.0, rng=utils.RandomUniform(0, 1).rand, 
18           sort=False, normalise=False): 
19      """Generates a random p-by-1 vector. 
20   
21      shape : A tuple. The shape of the underlying data. E.g., beta may represent 
22              an underlying 2-by-3-by-4 image, and will in that case be 24-by-1. 
23   
24      density : A scalar in (0, 1]. The density of the returned regression vector 
25              (fraction of non-zero elements). Zero-elements will be randomly 
26              distributed in the vector. Default is 1.0. 
27   
28      rng : The random number generator. Must be a function that takes *shape as 
29              input. Default is utils.RandomUniform in the interval [0, 1). 
30   
31      sort : A boolean. Whether or not to sort the vector. The vector is sorted 
32              along the dimensions in order from the first. Default is False. 
33   
34      normalise : A boolean. Whether or not to normalise the vector. Default is 
35              False. 
36      """ 
37      if not isinstance(shape, (list, tuple)): 
38          shape = (shape,) 
39   
40      density = max(0.0, min(density, 1.0)) 
41   
42      p = np.prod(shape) 
43      ps = int(density * p + 0.5) 
44   
45      beta = rng(p) 
46      beta[ps:] = 0.0 
47      beta = np.random.permutation(beta) 
48   
49      if sort: 
50          beta = np.reshape(beta, shape) 
51          for i in xrange(len(shape)): 
52              beta = np.sort(beta, axis=i) 
53   
54      beta = np.reshape(beta, (p, 1)) 
55   
56      if normalise: 
57          beta *= 1.0 / utils.norm2(beta) 
58   
59      return beta 
60   
61  if __name__ == "__main__": 
62      import doctest 
63      doctest.testmod() 
64