Question

我正在尝试让Stata选择每个人（ice_cream，Amanda，Christian）吃掉Paola的最小值，这样我最终只有3行：

person  ice_cream
    Amanda  16
    Amanda  27
    Amanda  29
    Amanda  40
    Amanda  96
    Amanda  97
    Christian   19
    Christian   23
    Christian   26
    Christian   27
    Christian   28
    Christian   34
    Christian   62
    Christian   70
    Christian   78
    Paola   5
    Paola   11
    Paola   28
    Paola   97

Answer 1

避免创建新变量的答案：

sort person ice_cream
by person: keep if _n == 1

Answer 2

单线解决方案

collapse (min) ice_cream, by(person)

Answer 3

这应该有效：

* Generate a variable with the group minimums    
sort person
by person: egen Min = min(ice_cream)
* Only keep observations with same value as group minimums
keep if Min == ice_cream
* Delete minimum variable
drop Min

注意：这将只留下ice_cream最小值的观察值。如果组中的多个观察值具有ice_cream的最小值，那么您将对该组有多个观察值（请注意，这不在上述数据中，但如果例如ice_cream是因子变量则可能是这样）。如果您想要每组进行一次独特的观察，那么您可以添加：

duplicates drop person, force

Answer 4

如果您只想显示ice_cream吃过的最小值通过Amanda，Christian和Paola，但没有更改数据集，您可以改为使用summarize命令：

clear

input str20 person ice_cream
Amanda  16
Amanda  27
Amanda  29
Amanda  40
Amanda  96
Amanda  97
Christian   19
Christian   23
Christian   26
Christian   27
Christian   28
Christian   34
Christian   62
Christian   70
Christian   78
Paola   5
Paola   11
Paola   28
Paola   97
end

bysort person: summarize ice_cream

---------------------------------------------------------------------------
-> person = Amanda

    Variable |        Obs        Mean    Std. Dev.       Min        Max
-------------+---------------------------------------------------------
   ice_cream |          6    50.83333    36.18517         16         97

---------------------------------------------------------------------------
-> person = Christian

    Variable |        Obs        Mean    Std. Dev.       Min        Max
-------------+---------------------------------------------------------
   ice_cream |          9    40.77778    22.63171         19         78

---------------------------------------------------------------------------
-> person = Paola

    Variable |        Obs        Mean    Std. Dev.       Min        Max
-------------+---------------------------------------------------------
   ice_cream |          4       35.25    42.30347          5         97

选择最小的观察块

4 个答案: