R语言随机抽样

本是古典何须时尚 2023-07-24 14:50 40阅读 0赞

*  简单随机抽样是指从总体N个单位中任意抽取n个单位作为样本，使每个可能的样本被抽中的概率相等的一种抽样方式
 *  可通过srswr函数，srswor和sample函数实现
 *  srswr函数和srswor函数在sampling包中，使用前需要先**加载sampling包**  
    **srswr(n, N)  
    srswor(n, N)  
    sample(x, size, replace = FALSE, prob = NULL)**  
    **示例：**

--------------------

# 有放回的简单随机抽样-srswr函数 #

**srswr(n, N)**  
srswr函数可实现放回简单随机抽样，表示在总体N中有放回地抽取n个样本，返回一个长度为N的向量，每个分量的值表示抽取次数  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_0_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzMTMzMTky_size_1_color_FFFFFF_t_70]  
**示例：**

install.packages("sampling")
    #  运行结果：
    #  WARNING: Rtools is required to build R packages but is not currently installed. Please download and install the appropriate version of Rtools before proceeding:
    #  
    #  https://cran.rstudio.com/bin/windows/Rtools/
    #  Installing package into ‘C:/Users/Admin/Documents/R/win-library/3.6’
    #  (as ‘lib’ is unspecified)
    #  also installing the dependency ‘lpSolve’
    #  
    #  试开URL’https://cran.rstudio.com/bin/windows/contrib/3.6/lpSolve_5.6.15.zip'
    #  Content type 'application/zip' length 748088 bytes (730 KB)
    #  downloaded 730 KB
    #  
    #  试开URL’https://cran.rstudio.com/bin/windows/contrib/3.6/sampling_2.8.zip'
    #  Content type 'application/zip' length 905090 bytes (883 KB)
    #  downloaded 883 KB
    #  
    #  package ‘lpSolve’ successfully unpacked and MD5 sums checked
    #  package ‘sampling’ successfully unpacked and MD5 sums checked
    #  
    #  The downloaded binary packages are in
    #  	       C:\Users\Admin\AppData\Local\Temp\RtmpWuDkpt\downloaded_packages
    library(sampling)
    
    s <- srswr(8,100)
    s
    #  运行结果：
    #    [1] 0 0 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0
    #   [41] 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0 1 0 0 0 0 0 0 0
    #   [81] 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
    obs <- c(1:100)[s!=0]
    obs
    #  运行结果：
    #  [1]  4  6 29 44 67 69 73 92
    n <- s[s!=0]
    n
    #  运行结果：
    #  [1] 1 1 1 1 1 1 1 1

# 不放回简单随机抽样-srswor函数 #

**srswor(n, N)**  
srswor函数实现不放回简单随机抽样，表示在总体N中无放回地抽取n个样本，返回一个长度为N的向量，每个分量的值表示抽取次数，取值为0或1  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_0_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzMTMzMTky_size_1_color_FFFFFF_t_70 1]  
**示例：**

install.packages("sampling")
    #  运行结果：
    #  WARNING: Rtools is required to build R packages but is not currently installed. Please download and install the appropriate version of Rtools before proceeding:
    #  
    #  https://cran.rstudio.com/bin/windows/Rtools/
    #  Installing package into ‘C:/Users/Admin/Documents/R/win-library/3.6’
    #  (as ‘lib’ is unspecified)
    #  also installing the dependency ‘lpSolve’
    #  
    #  试开URL’https://cran.rstudio.com/bin/windows/contrib/3.6/lpSolve_5.6.15.zip'
    #  Content type 'application/zip' length 748088 bytes (730 KB)
    #  downloaded 730 KB
    #  
    #  试开URL’https://cran.rstudio.com/bin/windows/contrib/3.6/sampling_2.8.zip'
    #  Content type 'application/zip' length 905090 bytes (883 KB)
    #  downloaded 883 KB
    #  
    #  package ‘lpSolve’ successfully unpacked and MD5 sums checked
    #  package ‘sampling’ successfully unpacked and MD5 sums checked
    #  
    #  The downloaded binary packages are in
    #  	       C:\Users\Admin\AppData\Local\Temp\RtmpWuDkpt\downloaded_packages
    library(sampling)
    
    LETTERS
    #  运行结果：
    #   [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" "T"
    #  [21] "U" "V" "W" "X" "Y" "Z"
    s <- srswor(10, 26)
    s
    #  运行结果：
    #   [1] 1 1 0 1 0 0 0 0 0 1 0 0 1 0 0 0 1 0 0 1 1 1 0 1 0 0
    obs <- c(1:26)[s!=0]
    obs
    #  运行结果：
    #   [1]  1  2  4 10 13 17 20 21 22 24
    sample <- LETTERS[obs]
    sample
    #  运行结果：
    #   [1] "A" "B" "D" "J" "M" "Q" "T" "U" "V" "X"

# **sample函数** #

**sample****(x,****size****,** **replace** **= FALSE，****prob** **= NULL）**  
sample函数可实现放回简单抽样和不放回简单随机抽样，返回随机抽样得到的元素。同时也可对数据进行随机分组

<table> 
 <thead> 
  <tr> 
   <th align="left">参数</th> 
   <th align="left">描述</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="left">x</td> 
   <td align="left">数据</td> 
  </tr> 
  <tr> 
   <td align="left">size</td> 
   <td align="left">抽取样本数</td> 
  </tr> 
  <tr> 
   <td align="left">replace</td> 
   <td align="left">replace = FALSE 为不放回随机抽样；replace = TRUE 为放回随机抽样</td> 
  </tr> 
  <tr> 
   <td align="left">prob</td> 
   <td align="left">权重向量</td> 
  </tr> 
 </tbody> 
</table>

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_0_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQzMTMzMTky_size_1_color_FFFFFF_t_70 2]  
**示例：**

LETTERS
    #  运行结果：
    #   [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" "T"
    #  [21] "U" "V" "W" "X" "Y" "Z"
    sample(LETTERS,5,replace = TRUE)   #  有放回
    #  运行结果：
    #  [1] "C" "M" "L" "K" "N"
    sample(LETTERS,5,replace = FALSE)   #  无放回
    #  运行结果：
    #  [1] "X" "G" "H" "B" "J"
    n <- sample(c(1:2),26,replace = TRUE,prob = c(0.7, 0.3))
    n
    #  运行结果：
    #  [1] 2 1 2 1 1 1 1 1 1 2 2 2 2 1 2 1 1 1 1 1 1 2 1 1 2 1
    sample1 <- LETTERS[n==1]
    sample1
    #  运行结果：
    #  [1] "B" "D" "E" "F" "G" "H" "I" "N" "P" "Q" "R" "S" "T" "U" "W" "X" "Z"
    sample2 <- LETTERS[n==2]
    sample2
    #  运行结果：
    #  [1] "A" "C" "J" "K" "L" "M" "O" "V" "Y"

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