sum price retu list
g cv=r(sd)/r(mean) di cv
. sysuse auto,clear(1978 Automobile Data). sum price Variable Obs Mean Std. Dev. Min Max price 74 6165.257 2949.496 3291 15906. retu listscalars: r(N) = 74 r(sum_w) = 74 r(mean) = 6165.256756756757 r(Var) = 8699525.974268789 r(sd) = 2949.495884768919 r(min) = 3291 r(max) = 15906 r(sum) = 456229. g cv=r(sd)/r(mean). di cv.47840601
2.
sysuse auto,clear reg mpg price weight g r2 = e(mss)/(e(mss)+e(rss)) di r2
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. sysuse auto,clear(1978 Automobile Data). . reg mpg price weight, 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 . . g r2 = e(mss)/(e(mss)+e(rss)). . di r2.65314466
3.
sysuse auto, clear
global varlist mpg price weight sum $varlist
local varlist mpg price weight sum `varlist’
. global varlist mpg price weight. . sum $varlist Variable Obs Mean Std. Dev. Min Max mpg 74 21.2973 5.785503 12 41 price 74 6165.257 2949.496 3291 15906 weight 74 3019.459 777.1936 1760 4840. . local varlist mpg price weight. . sum `varlist' Variable Obs Mean Std. Dev. Min Max mpg 74 21.2973 5.785503 12 41 price 74 6165.257 2949.496 3291 15906 weight 74 3019.459 777.1936 1760 4840
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4.
cap drop sum qui generate sum=0
foreach var of varlist headroom length { } sum sum
. cap drop sum. . qui generate sum=0. . foreach var of varlist headroom length { 2. . qui replace sum = sum + `var' 3. . }. . sum sum Variable Obs Mean Std. Dev. Min Max sum 74 190.9257 22.71468 145 236.5qui replace sum = sum + `var’
第二章 数据管理和画图
2.1数据类型和格式
内部数值型数据有五种模式 存在类型 byte int long float
字节数 1 2 4 4 8
最小 -127
最大 100 32,740 2,147,483,620 1.70141173319х1038 8.9984656743х10307
-32,767
-2,147,483,647
-1.70141173319х1038 -8.9984656743х10307
double
另外，还有字符型数据，与其相关的两条命令是destring，将字符型变量转变为数值型，tostring则将数值型转化为字符型。encode/decode
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数据显示格式可以利用命令format来进行调整，具体参数有 f g e c
固定形式 一般形式 指数形式 千分位加豆号
.2f 3.5555 3.56
可以利用命令help format了解数据显示格式的更多内容。
2.2 数据输入
use import excel insheet odbc
infile (free format) infix (fixed format) import sasxport haver xmluse
Stata格式数据的输入 use filename [, clear nolabel]
use [varlist] [if] [in] using filename [, clear nolabel] 例：use auto, clear
use if foreign==1 using auto, clear 输入文本文件数据
insheet [varlist] using filename [, options] [no]double override default storage type tab tab-delimited data
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comma comma-delimited data delimiter(\ clear replace data in memory case preserve variable name's case
[no]names variable names are included on the first line of the file 例：
insheet using [path] gdp.txt, clear ….
ODBC 调入ACCESS文件（工业企业数据）
c:\\Windows\\SysWoW64\\odbcad32
odbc load, table(“QY05”)
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