Stata（一）

Stata官网帮助文档汇总：https://www.stata.com/features/documentation/

The complete contents for all manuals: https://www.stata.com/manuals/icombinedsubjecttableofcontents.pdf

[1]排序：（默认升序）

gsort A B

A, B 列名

主要关键字：A 

次要关j键字：B

egen C = min(B), by(A)

令C中每个个体的各个观测值等于A列对应的每个个体最小的变量B的观测值。按照A列升序排列。

Stata has two built-in variables called _n and _N. 

_n is Stata notation for the current observation number. _n is 1 in the first observation, 2 in the second, 3 in the third, and so on.

_N is Stata notation for the total number of observations.

When _n is combined with by, however, _n is the observation number within by-group

Example:  

set obs 10

generate x = rnormal()

sort x

by x: generate cum = _N if _n==1

显示：

       x    cum
-2.260383 1
-1.975356 1
-1.735899 1
-1.655572 1
-1.585099 1

price 变量中最小的前10个数：

gsort +price 

list make price in 1/10