基于matlab实现fpGrown算法

fpGrowth算法是一种用于挖掘频繁模式的算法，其核心思想是利用FP树来表示事务数据，并通过不断地拆分FP树来发现频繁模式。在Matlab中实现fpGrowth算法需要实现以下步骤：

创建FP树：读入事务数据，创建空的FP树。遍历每个事务记录，将其中的项目按照出现频率从高到低排序，并插入FP树中。
构建频繁项头表：遍历FP树中的每个节点，记录其出现频率，并将相同出现频率的节点链接在一起，形成频繁项头表。
挖掘频繁模式：从频繁项头表中选择一个频繁项，然后遍历其链表，得到该频繁项的条件模式基。对条件模式基递归地构建新的FP树，并继续挖掘频繁项，直到无法找到新的频繁项为止。

以下是Matlab代码实现fpGrowth算法的主要步骤：

% 1. 创建FP树 fpTree = createFPTree(transactions);

% 2. 构建频繁项头表 freqItems = buildFreqItems(fpTree);

% 3. 挖掘频繁模式 frequentPatterns = mineFrequentPatterns(freqItems, minSupp);

% 定义创建FP树的函数 function fpTree = createFPTree(transactions) fpTree = struct('item', [], 'count', 0, 'children', {}, 'next', []); for i = 1:length(transactions) transaction = transactions{i}; sortedTransaction = sortTransaction(transaction); currentNode = fpTree; for j = 1:length(sortedTransaction) item = sortedTransaction(j); childNode = findChildNode(currentNode, item); if isempty(childNode) childNode = struct('item', item, 'count', 0, 'children', {}, 'next', []); currentNode.children = [currentNode.children, childNode]; childNode.next = findNextNode(currentNode, item); end childNode.count = childNode.count + 1; currentNode = childNode; end end end

% 定义构建频繁项头表的函数 function freqItems = buildFreqItems(fpTree) freqItems = struct('item', [], 'count', 0, 'nodeLink', []); freqItemMap = containers.Map(); for i = 1:length(fpTree.children) currentNode = fpTree.children(i); while ~isempty(currentNode) item = currentNode.item; count = currentNode.count; if isKey(freqItemMap, item) freqItem = freqItemMap(item); freqItem.count = freqItem.count + count; else freqItem = struct('item', item, 'count', count, 'nodeLink', []); freqItemMap(item) = freqItem; end currentNode = currentNode.next; end end freqItemKeys = keys(freqItemMap); for i = 1:length(freqItemKeys) freqItem = freqItemMap(freqItemKeys{i}); freqItems = [freqItems, freqItem]; end freqItems = sortFreqItems(freqItems); end

% 定义挖掘频繁模式的函数 function frequentPatterns = mineFrequentPatterns(freqItems, minSupp) frequentPatterns = {}; for i = 1:length(freqItems) freqItem = freqItems(i); if freqItem.count >= minSupp frequentPatterns = [frequentPatterns, freqItem.item]; conditionalFPTree = createConditionalFPTree(freqItem, freqItems); conditionalFreqItems = buildFreqItems(conditionalFPTree); conditionalFrequentPatterns = mineFrequentPatterns(conditionalFreqItems, minSupp); for j = 1:length(conditionalFrequentPatterns) frequentPatterns = [frequentPatterns, [freqItem.item, conditionalFrequentPatterns{j}]]; end end end end

% 定义辅助函数 function sortedTransaction = sortTransaction(transaction) [sortedTransaction, index] = sort(transaction); [~, inverseIndex] = sort(index); sortedTransaction = sortedTransaction(inverseIndex); end

function childNode = findChildNode(currentNode, item) childNode = []; for i = 1:length(currentNode.children) if currentNode.children(i).item == item childNode = currentNode.children(i); break; end end end

function nextNode = findNextNode(currentNode, item) nextNode = []; while ~isempty(currentNode.next) currentNode = currentNode.next; if currentNode.item == item nextNode = currentNode; break; end end end

function sortedFreqItems = sortFreqItems(freqItems) [~, index] = sort([freqItems.count], 'descend'); sortedFreqItems = freqItems(index); end

function conditionalFPTree = createConditionalFPTree(freqItem, freqItems) conditionalFPTree = struct('item', [], 'count', 0, 'children', {}, 'next', []); freqItemNode = freqItem.nodeLink; while ~isempty(freqItemNode) transaction = freqItemNode.transaction; count = freqItemNode.count; sortedTransaction = sortTransaction(transaction); currentNode = conditionalFPTree; for i = 1:length(sortedTransaction) item = sortedTransaction(i); if ismember(item, [freqItems.item]) childNode = findChildNode(currentNode, item); if isempty(childNode) childNode = struct('item', item, 'count', 0, 'children', {}, 'next', []); currentNode.children = [currentNode.children, childNode]; childNode.next = findNextNode(currentNode, item); end childNode.count = childNode.count + count; currentNode = childNode; end end freqItemNode = freqItemNode.next; end end

function freqItem = findFreqItem(freqItems, item) freqItem = []; for i = 1:length(freqItems) if freqItems(i).item == item freqItem = freqItems(i); break; end end en