Yuhang's Blog

数位DP

问题类型是求解小于等于某个给定$n$的、数位符合一定条件的的正整数的个数。注意如果题目要求是求解某个正整数区间上的、符合一定条件的数的个数，则可以轻易化归到上述问题。 Read more

Coding

Support Vector Machines

We could use KNN, logistic regression, LDA, and decision trees for classification problems. Here we discuss a new set of methods: the maximal margin classifier, the support vector classifier, and the support vector machine, which are often loosely referred to as “support vector machines”. Read more

Mathematics

Tree-Based Methods

Recall that we use step functions, where the range of predictor $X$ is broken into several bins and in each bin the average of the observed response, certainly a constant, is used as the prediction. Step functions can be viewed as a special case of tree-based methods, the latter of which could be applied to multiple predictors. Read more

Mathematics

Non-Linear Models

Linear models, including linear regression and models making improvements on it, can only offer a limited approximation of the real world. Therefore, moving beyond linearity is necessitated in various situations where more flexibility is required. Read more

Mathematics