hashtable - Stata 简单键值对

Question

我正在使用一组命名规则定义分类变量。我想将这些规则作为“参数”放在序言中，以后可以轻松更改。我想知道最好的方法来做到这一点。我觉得这里不需要可重现的示例，因为我在问——一般来说——在 Stata 中设置本质上具有键值结构的参数的好方法是什么？

这是我目前正在使用的代码，用于根据天气事件的虚拟变量对日期进行分类。

preserve 
clear
input str12 key str40 val
"Clear"         "!(event_thunder|event_snow|event_rain)"
"Rain"          "event_rain & !(event_thunder|event_snow)"
"Snow"          "event_snow & !(event_thunder|event_rain)"
"Rain & Snow"   "(event_snow & event_rain) & !event_thunder"
"Thunder"       "event_thunder"
end

scalar N_events = _N

forvalues i = 1/`=N_events'{
    scalar  event_key`i' = key[`i']
    scalar  event_val`i' = val[`i']
}
restore

在代码的后面，我可以迭代我的“key”和“val”标量来定义我的分类变量。

gen byte event = 0
forvalues i = 1/`=N_events'{
    local event_condition `=event_val`i''
    replace event = `i' if `event_condition'
}

我仍然没有找到使用我的 event_key* 标量应用标签的正确代码。也欢迎就此提出任何建议。

Answer 1

你的代码，经过一些调整，等同于这个例子:

clear
set more off

sysuse auto
keep make price foreign

preserve

    clear

    input str12 key str40 val
    "for_cheap"         "foreign & price < 10000"
    "hom_expen"         "!foreign & price >= 10000"
    end

    local numkeys = _N

    forvalues i = 1/`numkeys' {
        local  event_key`i' = key[`i']
        local  event_val`i' = val[`i']
    }

restore 

gen byte event = 0
forvalues i = 1/`numkeys' {
    replace event = `i' if `event_val`i''
}

save testing, replace

但你只想要这个，它会产生完全相同的结果:

clear
set more off

sysuse auto
keep make price foreign

gen byte event = 0
replace event = 1 if foreign & price < 10000
replace event = 2 if !foreign & price >= 10000

// to test these results with previous
cf _all using testing, verbose

例如，您仍然可以将条件放在局部变量中，然后使用它:

<snip>

local for_cheap foreign & price < 10000
local hom_expen !foreign & price >= 10000

gen byte event = 0
replace event = 1 if `for_cheap'
replace event = 2 if `hom_expen'

此外，您可以使用循环而不是多个 replace:

<snip>

local for_cheap "foreign & price < 10000"
local hom_expen "!foreign & price >= 10000"

local allcond for_cheap hom_expen
local n : word count `allcond'

gen byte event = 0
forvalues i = 1/`n' {
    local cond `:word `i' of `allcond'' // extended macro function
    replace event = `i' if ``cond''

    // syntax for value labels
    local lbl `lbl' `i' "`cond'" 
}

label define lblevent `lbl'
label values event lblevent

list in 1/25

这将每个命名条件放在另一个名为 allcond 的本地中。然后使用 parallel lists策略循环。我还为值标签添加了代码。

另请参阅help extended_fcn 阅读扩展宏函数(我已经使用过)。

如果您只想声明键/值一次，您仍然可以只使用本地变量:

clear

sysuse auto
keep make price foreign

local allcond for_cheap "foreign & price < 10000" ///
              hom_expen "!foreign & price >= 10000"

local n : word count `allcond'

gen byte event = 0
forvalues i = 2(2)`n' {

    // get label and condition (extended macro function)
    local condlbl `:word `=`i'-1' of `allcond''
    local cond `:word `i' of `allcond'' 

    // replace
    replace event = `=`i'/2' if `cond'

    // syntax for value labels
    local lbl `lbl' `=`i'/2' "`condlbl'"  
}

label define lblevent `lbl'
label values event lblevent

但在这一点上，您使用数据库的策略(以及我的等效代码)更容易阅读。

顺便说一下，根据您的其余代码，您可能可以避免preserve/restore。您可以先输入键/值，然后加载工作数据库:

clear
set more off

// input key/val database

input str12 key str40 val
"for_cheap"         "foreign & price < 10000"
"hom_expen"         "!foreign & price >= 10000"
end

local numkeys = _N

forvalues i = 1/`numkeys' {
    local  event_key`i' = key[`i']
    local  event_val`i' = val[`i']
}

// load working database

clear

sysuse auto
keep make price foreign

gen byte event = 0
forvalues i = 1/`numkeys' {
    replace event = `i' if `event_val`i''
}

list