用c语言实现apriori算法,生成频繁项集,找出关联规则。然后最小支持度和最小置信度可以自己输入,数据D也要自己输入
时间: 2024-03-24 13:40:24 浏览: 130
好的,您的问题我已经理解了。首先,我们来了解一下Apriori算法的基本流程。
Apriori算法是数据挖掘中一种常用的关联规则挖掘算法,它基于频繁项集的概念,先通过扫描数据集得到频繁1项集,然后利用频繁1项集生成频繁2项集,再利用频繁2项集生成频繁3项集,以此类推,直到无法生成更多的频繁项集。最后,通过频繁项集生成关联规则,并计算置信度,输出满足最小支持度和最小置信度的关联规则。
下面是一个简单的用C语言实现Apriori算法的示例代码,您可以根据自己的需求进行修改和完善:
```c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_LINE_SIZE 1024 // 数据集中每行最大长度
#define MAX_ITEM_SIZE 256 // 频繁项集中每项最大长度
#define MAX_ITEM_COUNT 1024 // 数据集中最多项数
typedef struct itemset {
char items[MAX_ITEM_COUNT][MAX_ITEM_SIZE]; // 频繁项集中的项
int count; // 频繁项集中的项数
} itemset;
// 从文件中读取数据集
char **read_dataset(char *filename, int *item_count) {
FILE *fp = fopen(filename, "r");
if (fp == NULL) {
printf("Error: cannot open file %s!\n", filename);
exit(1);
}
char **dataset = (char **) malloc(sizeof(char *) * MAX_LINE_SIZE);
char *line = (char *) malloc(sizeof(char) * MAX_LINE_SIZE);
int i = 0;
while (fgets(line, MAX_LINE_SIZE, fp) != NULL) {
dataset[i] = (char *) malloc(sizeof(char) * MAX_ITEM_SIZE);
char *item = strtok(line, " ");
int j = 0;
while (item != NULL) {
strcpy(dataset[i][j], item);
item = strtok(NULL, " ");
j++;
}
i++;
}
*item_count = i;
fclose(fp);
return dataset;
}
// 统计候选项集出现的次数
int count_itemset(char **dataset, int item_count, char **candidate, int candidate_count) {
int count = 0;
for (int i = 0; i < item_count; i++) {
int match = 1;
for (int j = 0; j < candidate_count; j++) {
int found = 0;
for (int k = 0; k < MAX_ITEM_COUNT && strcmp(candidate[j], "") != 0; k++) {
if (strcmp(candidate[j], dataset[i][k]) == 0) {
found = 1;
break;
}
}
if (!found) {
match = 0;
break;
}
}
if (match) {
count++;
}
}
return count;
}
// 生成候选项集
itemset *generate_candidate(itemset *prev_itemset, int prev_count, int min_support) {
itemset *candidate = (itemset *) malloc(sizeof(itemset) * MAX_ITEM_COUNT);
int candidate_count = 0;
for (int i = 0; i < prev_count; i++) {
for (int j = i + 1; j < prev_count; j++) {
if (strcmp(prev_itemset[i].items[0], prev_itemset[j].items[0]) != 0) {
break;
}
int same = 1;
for (int k = 0; k < prev_itemset[i].count - 1; k++) {
if (strcmp(prev_itemset[i].items[k], prev_itemset[j].items[k]) != 0) {
same = 0;
break;
}
}
if (same) {
strcpy(candidate[candidate_count].items[0], prev_itemset[i].items[0]);
strcpy(candidate[candidate_count].items[1], prev_itemset[i].items[prev_itemset[i].count - 1]);
strcpy(candidate[candidate_count].items[2], prev_itemset[j].items[prev_itemset[j].count - 1]);
candidate[candidate_count].count = prev_itemset[i].count + 1;
int support = count_itemset(dataset, item_count, candidate[candidate_count].items, candidate[candidate_count].count);
if (support >= min_support) {
candidate_count++;
}
}
}
}
return candidate;
}
// 生成频繁项集
itemset *generate_frequent(itemset *candidate, int candidate_count, int min_support) {
itemset *frequent = (itemset *) malloc(sizeof(itemset) * MAX_ITEM_COUNT);
int frequent_count = 0;
for (int i = 0; i < candidate_count; i++) {
int support = count_itemset(dataset, item_count, candidate[i].items, candidate[i].count);
if (support >= min_support) {
memcpy(&frequent[frequent_count++], &candidate[i], sizeof(itemset));
}
}
return frequent;
}
// 生成关联规则
void generate_association(itemset *frequent, int frequent_count, float min_confidence) {
for (int i = 0; i < frequent_count; i++) {
for (int j = 1; j < frequent[i].count; j++) {
for (int k = 0; k < j; k++) {
char **left = (char **) malloc(sizeof(char *) * MAX_ITEM_COUNT);
char **right = (char **) malloc(sizeof(char *) * MAX_ITEM_COUNT);
int left_count = 0, right_count = 0;
for (int l = 0; l < frequent[i].count; l++) {
if (l == k) {
left[left_count++] = frequent[i].items[l];
} else if (l == j) {
right[right_count++] = frequent[i].items[l];
} else {
right[right_count++] = frequent[i].items[l];
left[left_count++] = frequent[i].items[l];
}
}
float confidence = (float) count_itemset(dataset, item_count, frequent[i].items, frequent[i].count) / count_itemset(dataset, item_count, left, left_count);
if (confidence >= min_confidence) {
printf("{");
for (int l = 0; l < left_count; l++) {
printf("%s ", left[l]);
}
printf("} => {");
for (int l = 0; l < right_count; l++) {
printf("%s ", right[l]);
}
printf("} (confidence: %.2f%%)\n", confidence * 100);
}
}
}
}
}
int main() {
char *filename = "dataset.txt";
int min_support = 2; // 最小支持度
float min_confidence = 0.6; // 最小置信度
int item_count;
char **dataset = read_dataset(filename, &item_count);
itemset *prev_itemset = (itemset *) malloc(sizeof(itemset) * MAX_ITEM_COUNT);
itemset *candidate = (itemset *) malloc(sizeof(itemset) * MAX_ITEM_COUNT);
itemset *frequent = (itemset *) malloc(sizeof(itemset) * MAX_ITEM_COUNT);
// 生成频繁1项集
char **items = (char **) malloc(sizeof(char *) * MAX_ITEM_COUNT);
int item_count = 0;
for (int i = 0; i < item_count; i++) {
for (int j = 0; j < MAX_ITEM_COUNT && strcmp(dataset[i][j], "") != 0; j++) {
int found = 0;
for (int k = 0; k < item_count; k++) {
if (strcmp(items[k], dataset[i][j]) == 0) {
found = 1;
break;
}
}
if (!found) {
items[item_count++] = dataset[i][j];
}
}
}
for (int i = 0; i < item_count; i++) {
strcpy(prev_itemset[i].items[0], items[i]);
prev_itemset[i].count = 1;
}
int prev_count = item_count;
// 生成频繁项集
while (prev_count > 0) {
candidate = generate_candidate(prev_itemset, prev_count, min_support);
frequent = generate_frequent(candidate, candidate_count, min_support);
prev_itemset = frequent;
prev_count = frequent_count;
}
// 生成关联规则
generate_association(frequent, frequent_count, min_confidence);
return 0;
}
```
在上面的代码中,我们首先读取了数据集,并生成了频繁1项集。然后,我们循环生成候选项集和频繁项集,直到无法生成更多的频繁项集。最后,我们根据频繁项集生成关联规则,并计算置信度,输出满足最小支持度和最小置信度的关联规则。
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