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Begin Stratified KFold

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This commit is contained in:
Ricardo Montañana Gómez
2023-07-21 21:49:02 +02:00
parent a2622a4fb6
commit f6e154bc6e
6 changed files with 150 additions and 61 deletions
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68
src/Platform/Folding.cc
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@@ -1,21 +1,23 @@
#include "Folding.h"
#include <algorithm>
#include <map>
#include <random>
using namespace std;
KFold::KFold(int k, int n, int seed)
KFold::KFold(int k, int n, int seed) : k(k), n(n), seed(seed)
{
this->k = k;
this->n = n;
indices = vector<int>(n);
iota(begin(indices), end(indices), 0); // fill with 0, 1, ..., n - 1
shuffle(indices.begin(), indices.end(), default_random_engine(seed));
random_device rd;
default_random_engine random_seed(seed == -1 ? rd() : seed);
shuffle(indices.begin(), indices.end(), random_seed);
}
pair<vector<int>, vector<int>> KFold::getFold(int nFold)
{
if (nFold >= k || nFold < 0) {
throw invalid_argument("nFold (" + to_string(nFold) + ") must be less than k (" + to_string(k) + ")");
throw out_of_range("nFold (" + to_string(nFold) + ") must be less than k (" + to_string(k) + ")");
}
int nTest = n / k;
auto train = vector<int>();
@@ -28,4 +30,60 @@ pair<vector<int>, vector<int>> KFold::getFold(int nFold)
}
}
return { train, test };
}
StratifiedKFold::StratifiedKFold(int k, const vector<int>& y, int seed) :
k(k), seed(seed)
{
// n = y.size();
// map<int, vector<int>> class_to_indices;
// for (int i = 0; i < n; ++i) {
// class_to_indices[y[i]].push_back(i);
// }
// random_device rd;
// default_random_engine random_seed(seed == -1 ? rd() : seed);
// for (auto& [cls, indices] : class_to_indices) {
// shuffle(indices.begin(), indices.end(), random_seed);
// int fold_size = n / k;
// for (int i = 0; i < k; ++i) {
// int start = i * fold_size;
// int end = (i == k - 1) ? indices.size() : (i + 1) * fold_size;
// stratified_indices.emplace_back(indices.begin() + start, indices.begin() + end);
// }
// }
n = y.size();
stratified_indices.resize(k);
vector<int> class_counts(*max_element(y.begin(), y.end()) + 1, 0);
for (auto i = 0; i < n; ++i) {
class_counts[y[i]]++;
}
vector<int> class_starts(class_counts.size());
partial_sum(class_counts.begin(), class_counts.end() - 1, class_starts.begin() + 1);
vector<int> indices(n);
for (auto i = 0; i < n; ++i) {
int label = y[i];
stratified_indices[class_starts[label]] = i;
class_starts[label]++;
}
int fold_size = n / k;
int remainder = n % k;
int start = 0;
for (auto i = 0; i < k; ++i) {
int fold_length = fold_size + (i < remainder ? 1 : 0);
stratified_indices[i].resize(fold_length);
copy(indices.begin() + start, indices.begin() + start + fold_length, stratified_indices[i].begin());
start += fold_length;
}
}
pair<vector<int>, vector<int>> StratifiedKFold::getFold(int nFold)
{
if (nFold >= k || nFold < 0) {
throw out_of_range("nFold (" + to_string(nFold) + ") must be less than k (" + to_string(k) + ")");
}
vector<int> test_indices = stratified_indices[nFold];
vector<int> train_indices;
for (int i = 0; i < k; ++i) {
if (i == nFold) continue;
train_indices.insert(train_indices.end(), stratified_indices[i].begin(), stratified_indices[i].end());
}
return { train_indices, test_indices };
}