v21i04.R

代码详细解释了bagging方法的运用，以及包含了详细的bagging代码(The code explains the application of bagging method in detail, and contains detailed bagging code.)

说明：  R语言舍选法、极坐标法、Box-Muller变换产生正态随机变量(R Language Rounding Method, Polar Coordinate Method and Box-Muller Transform to Generate Normal Random Variables)

说明：  R语言舍选法、极坐标法、Box-Muller变换产生正态随机变量(R Language Rounding Method, Polar Coordinate Method and Box-Muller Transform to Generate Normal Random Variables)

双重差分估计 双重差分模型（difference-in-difference，DID）近年来多用于计量经济学中对于公共政策或项目实施效果 的定量评估。 通常大范围的公共政策有别于普通科研性研究，难以保证对于政策实施组和对照组在样本分配上的完全随机。非随机分配政策实施组和对照组的试验称为自然试验（naturaltrial），此类试验存在较显著的特点，即不同组间样本在政策实施前可能存在事前差异，仅通过单一前后对比或横向对比的分析方法会忽略这种差异，继而导致对政策实施效果的有偏估计。(Quantitative evaluation of policy or project implementation effect. Generally, a wide range of public policies is different from general scientific research, and it is difficult to ensure that the sample allocation for the policy implementation group and the control group is completely random. The non-randomly assigned policy implementation group and the control group are called natural trials, which have significant characteristics, i.e. there may be prior differences between the different groups of samples before the implementation of the policy, and this difference will be ignored only through a single pre-and post-comparison or horizontal comparison analysis method, which leads to the policy. Biased estimation of implementation)

混频回归模型的r语言包，里边包括例题啥的。(The package of midas (mixed frequecncy), which includes the concrete code of some examples.)

从plots文件中读取目标站点信息 从station文件读取气象站点信息 自动匹配距离目标站点最近的气象站名称(Automatically match the closest meteorogical station of subject plot.)

r语言配套分析的数据，代码。适合初学者进行使用(R language supporting analysis of data, code. Suitable for beginners)

水动力模型MIKE21数据后处理 dfsu格式文件导出模拟结果xyz格式文件 R语言可以迅速批量读取xyz文件，并根据文件名排序 以便于后期处理(MIKE 21 export results from dsfu R read numerous xyz files)

利用R语言SEM程序包进行通径分析，简单易学，容易上手(SEM path analysis model)

在R中如何导入数据，主要是txt，csv，excel等数据格式的导入(how to imput data in R)