cngcode converts Chinese addresses to latitude and longitude. cnaddress converts latitude and longitude to Chinese iconic geographical locations. cntraveltime can calculate the traffic distance between two geographical locations (you can even choose different traffic modes). cnmapsearch can search for various geographical keywords such as subway stations, hospitals, cafes, barbecue stalls, etc., within a few kilometers of a given location. These commands are convenient for empirical research on geography and transportation and have broad application prospects in finance, economics, and sociology.

I will demonstrate how lasso-type techniques can be used for prediction with linear, binary, and count outcomes. I will then show why these methods are effective and how they work. The increasing availability of high-dimensional data and increasing interest in more realistic functional forms have sparked a renewed interest in automated methods for selecting the covariates to include in a model. I discuss the promises and perils of model selection and pay special attention to some new estimators that provide reliable inference after model selection.

I will then introduce a modeling method for forecasting the epidemic trend of COVID-19 so as to better adjust the policy of the epidemic prevention and control of the situation. Finally, I will summarize the matters needing attention in the epidemic data analysis of the situation.