Point Cloud Library (PCL)  1.11.0
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 #include <pcl/common/io.h>
43 #include <pcl/type_traits.h>
44 
45 
46 ///////////////////////////////////////////////////////////////////////////////
47 template<typename PointT>
48 void
49 pcl::RandomSample<PointT>::applyFilter (std::vector<int> &indices)
50 {
51  std::size_t N = indices_->size ();
52  std::size_t sample_size = negative_ ? N - sample_ : sample_;
53  // If sample size is 0 or if the sample size is greater then input cloud size
54  // then return all indices
55  if (sample_size >= N)
56  {
57  indices = *indices_;
58  removed_indices_->clear ();
59  }
60  else
61  {
62  // Resize output indices to sample size
63  indices.resize (sample_size);
64  if (extract_removed_indices_)
65  removed_indices_->resize (N - sample_size);
66 
67  // Set random seed so derived indices are the same each time the filter runs
68  std::srand (seed_);
69 
70  // Algorithm S
71  std::size_t i = 0;
72  std::size_t index = 0;
73  std::vector<bool> added;
74  if (extract_removed_indices_)
75  added.resize (indices_->size (), false);
76  std::size_t n = sample_size;
77  while (n > 0)
78  {
79  // Step 1: [Generate U.] Generate a random variate U that is uniformly distributed between 0 and 1.
80  const float U = unifRand ();
81  // Step 2: [Test.] If N * U > n, go to Step 4.
82  if ((N * U) <= n)
83  {
84  // Step 3: [Select.] Select the next record in the file for the sample, and set n : = n - 1.
85  if (extract_removed_indices_)
86  added[index] = true;
87  indices[i++] = (*indices_)[index];
88  --n;
89  }
90  // Step 4: [Don't select.] Skip over the next record (do not include it in the sample).
91  // Set N : = N - 1.
92  --N;
93  ++index;
94  // If n > 0, then return to Step 1; otherwise, the sample is complete and the algorithm terminates.
95  }
96 
97  // Now populate removed_indices_ appropriately
98  if (extract_removed_indices_)
99  {
100  std::size_t ri = 0;
101  for (std::size_t i = 0; i < added.size (); i++)
102  {
103  if (!added[i])
104  {
105  (*removed_indices_)[ri++] = (*indices_)[i];
106  }
107  }
108  }
109  }
110 }
111 
112 #define PCL_INSTANTIATE_RandomSample(T) template class PCL_EXPORTS pcl::RandomSample<T>;
113 
114 #endif // PCL_FILTERS_IMPL_RANDOM_SAMPLE_H_
void applyFilter(std::vector< int > &indices) override
Sample of point indices.