讀取資料
## Loading required package: Ecfun
##
## Attaching package: 'Ecfun'
## The following object is masked from 'package:base':
##
## sign
##
## Attaching package: 'Ecdat'
## The following object is masked from 'package:datasets':
##
## Orange
分層抽樣
library(sampling)
set.seed(123)
sample <- strata(dta, stratanames=c("county"),size=c(1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1), method="srswor")
sample[,2]
## [1] 1 4 12 138 132 151 262 22 251 203 124 160 86 298 81 200 236 113 397
## [20] 156 73 288 77 284 255 92 195 104 213 393 287 133 134 363 344 308 313 394
## [39] 364 233 377 354 252 367 420
擷取抽樣到的樣本
dtac <- dta[c(1,4,12,138,132,151,262,22,251,203,124,160,86,298,81,200,236,113,397,156,73,288,77,284,255,92,195,104,213,393,287,133,134,363,344,308,313,394,364,233,377,354,252,367,420),c(2,3,16,17)]
str(dtac)
## 'data.frame': 45 obs. of 4 variables:
## $ county : Factor w/ 45 levels "Alameda","Butte",..: 1 2 6 29 11 25 19 42 15 9 ...
## $ district: Factor w/ 409 levels "Ackerman Elementary",..: 362 132 392 27 130 17 25 288 63 219 ...
## $ readscr : num 692 652 617 643 634 ...
## $ mathscr : num 690 644 616 646 654 ...
