. global xlist price weight. reg mpg $xlist, noheader mpg Coef. Std. Err. t P>|t| [95% Conf. Interval] price -.0000935 .0001627 -0.57 0.567 -.000418 .0002309 weight -.0058175 .0006175 -9.42 0.000 -.0070489 -.0045862 _cons 39.43966 1.621563 24.32 0.000 36.20635 42.67296
全局宏可以适用于Stata软件的整个期间。比如修改example.do，调整宏xlist，都会起作用的。 Example.do sysuse auto,clear su mpg price weight reg mpg $xlist reg mpg `xlist’
局部宏用local 进行定义，用`’进行引用（其中左引号通常在~键上，与通常的单引号是不同的）。
. local xlist price weight. reg mpg `xlist', noheader mpg Coef. Std. Err. t P>|t| [95% Conf. Interval] price -.0000935 .0001627 -0.57 0.567 -.000418 .0002309 weight -.0058175 .0006175 -9.42 0.000 -.0070489 -.0045862 _cons 39.43966 1.621563 24.32 0.000 36.20635 42.67296
另一个例子
. local y mpg. local x \. reg `y' `x', noheader mpg Coef. Std. Err. t P>|t| [95% Conf. Interval] price -.0000935 .0001627 -0.57 0.567 -.000418 .0002309 weight -.0058175 .0006175 -9.42 0.000 -.0070489 -.0045862 _cons 39.43966 1.621563 24.32 0.000 36.20635 42.67296
1.7 循环语句
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Stata的循环语句有三种：foreach、forvalues、while。foreach是根据列表中的每一项进行循环，forvalues是根据连续整数进行循环，while是根据用户的条件是否满足进行循环。 先看两处数据产生命令generate和replace，和随机数产生器runiform()。
. clear. set obs 100obs was 0, now 100. set seed 1234. generate x1=runiform(). generate x2=runiform(). generate x3=runiform(). generate x4=runiform(). generate sum=x1+x2+x3+x4
. summarize sum Variable Obs Mean Std. Dev. Min Max sum 100 1.909211 .5527524 .567311 3.092883
下面，我们分别用三种循环语句实现4个变量的求和。 首先用foreach
*foreach loop with a variable list quietly replace sum = 0
foreach var of varlist x1 x2 x3 x4 { }
summarize sum
. *foreach loop with a variable list. quietly replace sum = 0. foreach var of varlist x1 x2 x3 x4 { 2. quietly replace sum = sum +`var' 3. }. summarize sum Variable Obs Mean Std. Dev. Min Max sum 100 1.909211 .5527524 .5673109 3.092883quietly replace sum = sum +`var'
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下面用forvales quietly replace sum = 0 forvalues i=1(1)4 { }
summarize sum
. quietly replace sum = 0. forvalues i=1(1)4 { 2. quietly replace sum = sum + x`i' 3. }. summarize sum Variable Obs Mean Std. Dev. Min Max sum 100 1.909211 .5527524 .5673109 3.092883quietly replace sum = sum + x`i'
利用while命令 quietly replace sum = 0 local i=1 while `i'<=4 { }
summarize sum
. quietly replace sum = 0. local i=1. while `i'<=4 { 2. quietly replace sum = sum + x`i' 3. local i = `i' + 1 4. } . summarize sum Variable Obs Mean Std. Dev. Min Max sum 100 1.909211 .5527524 .5673109 3.092883quietly replace sum = sum + x`i' local i = `i' + 1
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1.8 有用的其他命令
用户手册中提出的每个人需要知道的最常用的42条命令 Getting online help [U] 4 Stata’s help and search facilities
help, hsearch, net search, search, findit
Keeping Stata up to date
ado, net, update [U] 28 Using the Internet to keep up to date adoupdate [R] adoupdate
Operating system interface
pwd, cd [D] cd
Using and saving data from disk
save, saveold [D] save use [D] use
append, merge [U] 22 Combining datasets compress [D] compress
Inputting data into Stata [U] 21 Inputting and importing data
import [D] import edit [D] edit
Basic data reporting
describe [D] describe codebook [D] codebook list [D] list browse [D] edit count [D] count inspect [D] inspect table [R] table
tabulate [R] tabulate oneway and [R] tabulate twoway
Data manipulation [U] 13 Functions and expressions
generate, replace [D] generate egen [D] egen
rename [D] rename, [D] rename group clear [D] clear
drop, keep [D] drop sort [D] sort
encode, decode [D] encode, destring/tostring recode
order [D] order
by [U] 11.5 by varlist: construct reshape [D] reshape
Keeping track of your work
log [U] 15 Saving and printing output—log files notes [D] notes
Convenience
display [R] display
[R] Base Reference Manual
[D] Data Management Reference Manual
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[G] Graphics Reference Manual [M] Mata Reference Manual
[MV] Multivariate Statistics Reference Manual [P] Programming Reference Manual
[ST] Survival Analysis and Epidemiological Tables Reference Maunal [SVY] Survey Data Reference Manual [TS] Time-Series Reference Manual
[XT] Longitudinal/Panel-Data Reference Manual
1.8 用户写的程序
比如ivreg2，psmatch2, 可以运用findit ivreg2并安装使用
1.9 参考文献
Baum, Christopher F. An Introduction to Modern Econometrics Using Stata
Cameron, A. C. and P. K. Trivedi, 2009, Microeconometrics Using Stata, Stata Press, Texas.
1.10 练习
1. 运用数据auto.dta，获得价格price的简单统计信息，并利用r()的储存的信息计算价格的 变异系数（即标准差除以平均值）。
2. 利用数据auto.dta，做mpg对price, weight的回归，并利用e()中储存的信息计算R2。
3. 利用数据auto.dta，定义一个全局宏变量 varlist，代替变量mpg, price, weight,并获得varlist所代表变量的简单统计信息，利用局部宏重复上述过程。
4. 利用数据auto.dta，利用循环语句foreach产生一个新的变量total，等于headroom和length的加和，并用summarize命令检验均值是否正确。
参考答案： 1.
sysuse auto, clear
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