Source Code for Module topo.patterns.random

 1  """ 
 2  Two-dimensional pattern generators drawing from various random distributions. 
 3   
 4  $Id: random.py 7861 2008-02-07 06:01:22Z ceball $ 
 5  """ 
 6  __version__='$Revision: 7861 $' 
 7   
 8  import numpy.oldnumeric.random_array as RandomArray 
 9   
10  from topo.base.parameterizedobject import ParamOverrides 
11  from topo.base.parameterclasses import Number,Parameter 
12  from topo.base.patterngenerator import PatternGenerator 
13  from topo.base.sheetcoords import SheetCoordinateSystem 
14   
15  from topo.outputfns.basic import IdentityOF 
16   
17   
18 -class RandomGenerator(PatternGenerator): 
19      """2D random noise pattern generator abstract class.""" 
20   
21      __abstract = True 
22   
23      # The standard x, y, and orientation variables are currently ignored, 
24      # so they aren't shown in auto-generated lists of parameters (e.g. in the GUI) 
25      x       = Number(precedence=-1) 
26      y       = Number(precedence=-1) 
27      size    = Number(precedence=-1) 
28      orientation   = Number(precedence=-1) 
29   
30 -    def _distrib(self,shape,pos): 
31          """Method for subclasses to override with a particular random distribution.""" 
32          raise NotImplementedError 
33       
34      # Optimization: We use a simpler __call__ method here to skip the 
35      # coordinate transformations (which would have no effect anyway) 
36 -    def __call__(self,**params_to_override): 
37          self._check_params(params_to_override) 
38          params = ParamOverrides(self,params_to_override) 
39   
40          shape = SheetCoordinateSystem(params['bounds'],params['xdensity'],params['ydensity']).shape 
41   
42          result = self._distrib(shape,params) 
43   
44          mask = params['mask'] 
45          if mask is not None: 
46              result*=mask 
47               
48          output_fn = params['output_fn'] 
49          if output_fn is not IdentityOF: # Optimization (but may not actually help) 
50              output_fn(result) 
51           
52          return result 
53   
54   
55   
56 -class UniformRandom(RandomGenerator): 
57      """2D uniform random noise pattern generator.""" 
58   
59 -    def _distrib(self,shape,params): 
60          return RandomArray.uniform(params['offset'], params['offset']+params['scale'], shape) 
61   
62   
63 -class GaussianRandom(RandomGenerator): 
64      """ 
65      2D Gaussian random noise pattern generator. 
66   
67      Each pixel is chosen independently from a Gaussian distribution 
68      of zero mean and unit variance, then multiplied by the given 
69      scale and adjusted by the given offset. 
70      """ 
71   
72      scale  = Number(default=0.25,softbounds=(0.0,2.0)) 
73      offset = Number(default=0.50,softbounds=(-2.0,2.0)) 
74   
75 -    def _distrib(self,shape,params): 
76          return params['offset']+params['scale']*RandomArray.standard_normal(shape) 
77