随机森林点云分类 c++代码

随机森林是一种强大的机器学习算法，可用于点云分类。以下是一个基本的随机森林点云分类的C代码示例：

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <math.h>

// 定义点云结构
typedef struct {
    float x, y, z;
    int label;
} PointCloud;

// 定义决策树结构
typedef struct {
    float threshold;
    int feature;
    int label;
    struct Node* left;
    struct Node* right;
} Node;

// 计算基尼指数
float calculateGiniIndex(PointCloud* pointcloud, int numPoints) {
    int numLabels = 0;
    int* labelCounts = (int*)calloc(numPoints, sizeof(int));

    for (int i = 0; i < numPoints; i++) {
        labelCounts[pointcloud[i].label]++;
    }

    float giniIndex = 1.0;
    for (int i = 0; i < numPoints; i++) {
        float probability = (float)labelCounts[i] / numPoints;
        giniIndex -= pow(probability, 2);
    }

    free(labelCounts);

    return giniIndex;
}

// 构建决策树
Node* buildDecisionTree(PointCloud* pointcloud, int numPoints, int numFeatures) {
    if (numPoints == 0) {
        return NULL;
    }

    float bestGiniIndex = INFINITY;
    float bestThreshold;
    int bestFeature;
    int* bestLeftIndices = (int*)calloc(numPoints, sizeof(int));
    int* bestRightIndices = (int*)calloc(numPoints, sizeof(int));
    int numBestLeftPoints = 0;
    int numBestRightPoints = 0;

    for (int feature = 0; feature < numFeatures; feature++) {
        for (int threshold = 0; threshold < 256; threshold++) {
            int* leftIndices = (int*)calloc(numPoints, sizeof(int));
            int* rightIndices = (int*)calloc(numPoints, sizeof(int));
            int numLeftPoints = 0;
            int numRightPoints = 0;

            for (int i = 0; i < numPoints; i++) {
                if (pointcloud[i].x < threshold) {
                    leftIndices[numLeftPoints] = i;
                    numLeftPoints++;
                } else {
                    rightIndices[numRightPoints] = i;
                    numRightPoints++;
                }
            }

            float giniIndex = (numLeftPoints * calculateGiniIndex(pointcloud, leftIndices)) +
                (numRightPoints * calculateGiniIndex(pointcloud, rightIndices)) / numPoints;

            if (giniIndex < bestGiniIndex) {
                bestGiniIndex = giniIndex;
                bestThreshold = threshold;
                bestFeature = feature;
                numBestLeftPoints = numLeftPoints;
                numBestRightPoints = numRightPoints;

                for (int i = 0; i < numLeftPoints; i++) {
                    bestLeftIndices[i] = leftIndices[i];
                }

                for (int i = 0; i < numRightPoints; i++) {
                    bestRightIndices[i] = rightIndices[i];
                }
            }

            free(leftIndices);
            free(rightIndices);
        }
    }

    Node* node = (Node*)malloc(sizeof(Node));
    node->threshold = bestThreshold;
    node->feature = bestFeature;
    node->label = -1;

    node->left = buildDecisionTree(pointcloud, numBestLeftPoints, numFeatures);
    node->right = buildDecisionTree(pointcloud, numBestRightPoints, numFeatures);

    free(bestLeftIndices);
    free(bestRightIndices);

    return node;
}

// 预测点的标签
int predictLabel(Node* root, float x, float y, float z) {
    if (root->label != -1) {
        return root->label;
    }

    if (x < root->threshold) {
        return predictLabel(root->left, x, y, z);
    } else {
        return predictLabel(root->right, x, y, z);
    }
}

int main() {
    // 模拟一些点
    PointCloud pointcloud[10];
    pointcloud[0].x = 0.1; pointcloud[0].y = 0.2; pointcloud[0].z = 0.3; pointcloud[0].label = 0;
    pointcloud[1].x = 0.4; pointcloud[1].y = 0.5; pointcloud[1].z = 0.6; pointcloud[1].label = 1;
    // ...
    // 添加更多点

    // 构建决策树
    Node* root = buildDecisionTree(pointcloud, 10, 3);

    // 预测新点的标签
    int predictedLabel = predictLabel(root, 0.7, 0.8, 0.9);

    printf("Predicted Label: %d\n", predictedLabel);

    // 释放内存
    free(root);

    return 0;
}

这段代码通过构建决策树来实现点云的分类。其中，构建决策树的方法基于Gini指数来选择最佳的分割特征和阈值。通过预测，可以为新的点分配一个标签。