First, C4.5C4.5 is a classification decision tree algorithm in machine learning algorithm, it is a decision tree (decision tree is a decision-making node of the organization like a tree, in fact, a inverted tree) core algorithm ID3 improved algorithm, so basically understand half decision tree construction method can construct it. The decision tree construction method is actually the selection of a good feature and the split point as the current node classification criteria. C4.5 compared to the ID3 improvements are: 1, with the information gain rate to select attributes. ID3 Select attributes are subtree information gain, there are many ways to define information, ID3 use entropy (entropy, entropy is a measure of purity), that is, the entropy of the change in value. And C4.5 uses the information gain rate. Yes, the difference is that one is information gain and one is information gain rate. In general, the rate is used to take balance, like the effect of variance, such as the role of two runners, a starting point is 10m/s, its 10s after the 20m/s; the other person is 1m/s, and its 1s is 2m/s. If the difference is tight, then two of the gap is very large, if the use of speed increase (acceleration, that is, 1m/s^2) to measure, 2 people are the same acceleration. Therefore, the C4.5 overcomes the insufficiency of the attribute that ID3 chooses the value when the information gain chooses the attribute. 2, in the tree construction process pruning, in the construction decision tree, those hanging several elements of the node, do not consider the best, otherwise easily lead to overfitting. 3, the non-discrete data can also be processed. 4. Be able to deal with incomplete data.Second, the K-means algorithm is K-means algorithmThe K-means algorithm algorithm is a clustering algorithm that divides n objects into K-divisions (K < N) according to their attributes. It is similar to the maximum expected algorithm for dealing with mixed normal distributions (fifth of the Ten algorithms), as they all try to find the center of natural clustering in the data. It assumes that the object attributes come from the space vector, and that the goal is to minimize the sum of the mean squared errors within each group.third, support vector machinesSupport Vector machines, the English-supported vector machine, referred to as SV Machine (generally referred to as SVM in the paper). It is a supervised learning method, which is widely used in statistical classification and regression analysis. Support Vector machines map vectors to a higher dimensional space, where a maximum interval of hyperspace is established in this space. Two parallel super-planes are built on both sides of the super plane separating the data, and the distance between the two parallel planes is maximized by separating the super plane. It is assumed that the larger the distance or gap between parallel planes, the smaller the total error of the classifier. An excellent guide is c.j.c Burges's "Pattern Recognition Support vector machine Guide". Van der Walt and Barnard compare support vector machines with other classifiers.Iv. the Apriori algorithmApriori algorithm is one of the most influential algorithms for mining Boolean association rule frequent itemsets. The core is the recursive algorithm based on the two-stage frequency set theory. The association rule belongs to single-dimension, single-Layer and Boolean association rules in classification. In this case, all itemsets with support degrees greater than the minimum support are called frequent itemsets, or frequency sets.v. Maximum expectation (EM) algorithmIn statistical computation, the maximal expectation (em,expectation–maximization) algorithm is the algorithm for finding the maximum likelihood estimation of parameters in the probability (probabilistic) model, in which the probabilistic model relies on the invisible hidden variables (latent VARIABL). The greatest expectations are often used in the field of data aggregation (clustering) for machine learning and computer vision.Liu, PageRankPageRank is an important part of Google's algorithm. The U.S. patent was granted in September 2001, and the patent owner is one of Google's founders, Larry Page. As a result, the page in PageRank is not a webpage, it refers to Paige, that is, the hierarchical method is named after page. PageRank measures the value of the site based on the number and quality of external links and internal links to the site. The concept behind PageRank is that each link to a page is a poll of that page, and the more links it has, the more votes are being voted on by other sites. This is called "link popularity" – A measure of how many people are willing to hook up their site to your site. The concept of PageRank is quoted as a quote from an academic paper-the more times people are quoted, the more authoritative it is to judge the paper.Seven, AdaBoostAdaBoost is an iterative algorithm whose core idea is to train different classifiers (weak classifiers) for the same training set, and then set up these weak classifiers to form a stronger final classifier (strong classifier). The algorithm itself is achieved by changing the distribution of data, which determines the weights of each sample based on the correctness of the classification of each sample in each training set and the accuracy of the last population classification. The new data set that modifies the weights is sent to the lower classifier for training, and finally the classifier that is trained each time is combined as the final decision classifier.Eight, knn:k-nearest neighbor classificationK Nearest neighbor (k-nearest NEIGHBOR,KNN) classification algorithm is a theoretically mature method and one of the simplest machine learning algorithms. The idea of this approach is that if a sample is in the K most similar in the feature space (that is, the nearest neighbor in the feature space) Most of the samples belong to a category, then the sample belongs to that category.IX, Naive BayesIn many classification models, the two most widely used classification models are decision tree (decision tree model) and naive Bayesian model (Naive Bayesian MODEL,NBC). Naive Bayesian model originates from classical mathematics theory, has a solid mathematical foundation, and stable classification efficiency. At the same time, the NBC model has few parameters to estimate, less sensitive to missing data, and simpler algorithm. In theory, the NBC model has the smallest error rate compared to other classification methods. But this is not always the case, because the NBC model assumes that the properties are independent of each other, and this hypothesis is often not true in practice, which has a certain effect on the correct classification of the NBC model. When the number of attributes is more or the correlation between attributes is large, the efficiency of the NBC model is inferior to the decision tree model. The performance of the NBC model is best when the attribute correlation is small.10. CART: Classification and regression treeCART, classification and Regression Trees. There are two key ideas under the classification tree: the first is the idea of recursively dividing the argument space, and the second idea is to prune it with validation data.
Ten classical algorithms for big data algorithms
