stata - 根据不同年份的 GDP 变量创建 "GDP in 1960"变量

Question

我对 Stata 还很陌生。

我有一组“国家 GDP 年”形式的观察结果。我想创建一个新变量GDP1960，它给出每个国家1960年每年的GDP:

USA     $100m   1960        USA    $100m  1960  $100m
USA     $200m   1965   -->  USA    $200m  1965  $100m
Canada  $60m    1960        Canada $60m   1960  $60m

实现这一点的正确语法是什么？ (我假设egen以某种神秘的方式参与其中)

Answer 1

您已找到解决方案 cond() ，但这里有一些建议，可以使您的数据建模更容易，并帮助您避免通过创建 rank 进行排序时可能出现的问题。变量(我已经得到了您在下面询问的 egen 解决方案):

将下面的代码粘贴到您的 do 文件编辑器中并运行它:

*---------------------------------BEGIN EXAMPLE
clear

inp str20 country str10 gdp year
"USA"     "$100m"   1960        
"USA"     "$200m"   1965     
"Canada"  "$60m"    1960 
"Canada"  "$120m"   1965
"USA"     "$250m"   1970
"Mexico"  "$90m"    1970  
"Canada"  "$800m"   1970     
"Mexico"  "$160m"    1960 
"Mexico"  "$220m"   1965
"Mexico"  "$350m"   1975
end

//1. destring gdp so that we can work with it
destring gdp,  ignore("$", "m") replace

//2. Create GDP for 1960 var:
    bys country: g x = gdp if year==1960
    bys country: egen gdp60 = max(x)
    drop x

    **you could also create balanced panels to see gaps in your data**
        preserve
    ssc install panels
    panels country year
    fillin country year
    li   //take a look at the results win. to see how filled panel data would look
        restore

//3. create a gdp variable for each year (reshape the dataset)
    drop gdp60
    reshape wide gdp, i(country) j(year)

    **much easier to use this format for modeling
    su gdp1970
     **here's a fake "outcome" or response variable to work with**
    g outcome =  500+int((1000-500+1)*runiform())
    anova outcome gdp1960-gdp1970  //or whatever makes sense for your situation
*---------------------------------END EXAMPLE