Point Cloud Library (PCL)  1.14.1-dev
random_sample.hpp
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34  * $Id: extract_indices.hpp 1897 2011-07-26 20:35:49Z rusu $
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37 
38 #ifndef PCL_FILTERS_IMPL_RANDOM_SAMPLE_H_
39 #define PCL_FILTERS_IMPL_RANDOM_SAMPLE_H_
40 
41 #include <pcl/filters/random_sample.h>
42 
43 
44 ///////////////////////////////////////////////////////////////////////////////
45 template<typename PointT>
46 void
48 {
49  std::size_t N = indices_->size ();
50  std::size_t sample_size = negative_ ? N - sample_ : sample_;
51  // If sample size is 0 or if the sample size is greater then input cloud size
52  // then return all indices
53  if (sample_size >= N)
54  {
55  indices = *indices_;
56  removed_indices_->clear ();
57  }
58  else
59  {
60  // Resize output indices to sample size
61  indices.resize (sample_size);
62  if (extract_removed_indices_)
63  removed_indices_->resize (N - sample_size);
64 
65  // Set random seed so derived indices are the same each time the filter runs
66  std::srand (seed_);
67 
68  // Algorithm S
69  std::size_t i = 0;
70  std::size_t index = 0;
71  std::vector<bool> added;
72  if (extract_removed_indices_)
73  added.resize (indices_->size (), false);
74  std::size_t n = sample_size;
75  while (n > 0)
76  {
77  // Step 1: [Generate U.] Generate a random variate U that is uniformly distributed between 0 and 1.
78  const float U = unifRand ();
79  // Step 2: [Test.] If N * U > n, go to Step 4.
80  if ((N * U) <= n)
81  {
82  // Step 3: [Select.] Select the next record in the file for the sample, and set n : = n - 1.
83  if (extract_removed_indices_)
84  added[index] = true;
85  indices[i++] = (*indices_)[index];
86  --n;
87  }
88  // Step 4: [Don't select.] Skip over the next record (do not include it in the sample).
89  // Set N : = N - 1.
90  --N;
91  ++index;
92  // If n > 0, then return to Step 1; otherwise, the sample is complete and the algorithm terminates.
93  }
94 
95  // Now populate removed_indices_ appropriately
96  if (extract_removed_indices_)
97  {
98  std::size_t ri = 0;
99  for (std::size_t i = 0; i < added.size (); i++)
100  {
101  if (!added[i])
102  {
103  (*removed_indices_)[ri++] = (*indices_)[i];
104  }
105  }
106  }
107  }
108 }
109 
110 #define PCL_INSTANTIATE_RandomSample(T) template class PCL_EXPORTS pcl::RandomSample<T>;
111 
112 #endif // PCL_FILTERS_IMPL_RANDOM_SAMPLE_H_
void applyFilter(Indices &indices) override
Sample of point indices.
IndicesAllocator<> Indices
Type used for indices in PCL.
Definition: types.h:133