Data.Manipulation.with.R 2014

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R语言数据操作，英文版。 PP.Data.Manipulation.with.R.Jan.2014.pdf (972.24 KB, 需要: 5 个论坛币)

2015-4-30 19:14:13 上传

Jaynal Abedin的英文版《R语言数据操作》
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关键词：manipulation ulation ATION Data With 艺术 Series

1. Factors from numeric variables
   
2. 
   
3. Numeric variables are convenient during statistical analysis, but sometimes we need to create categorical (factor) variables from numeric variables. We can create a limited number of categories from a numeric variable using a series of conditional statements, but this is not an efficient way to perform this operation. In R, cut is a generic command to create factor variables from numeric variables. In the following example, we will see how we can create factors from a numeric variable, using a series of conditional statements. We will also use the cut command to perform the same task.
   
4. 
   
5. # creating a numeric variable by taking 100 random numbers
   
6. # from normal distribution
   
7. set.seed(1234) # setting seed to reproduce the example
   
8. numvar <- rnorm(100)
   
9. 
   
10. # creating factor variable with 5 distinct category
    
11. 
    
12. num2factor <- cut(numvar,breaks=5)
    
13. class(num2factor)
    
14. [1] "factor"
    
15. levels(num2factor)
    
16. [1] "(-2.35,-1.37]"  "(-1.37,-0.389]" "(-0.389,0.592]" "(0.592,1.57]"   "(1.57,2.55]"
    
17. table(num2factor)
    
18. num2factor
    
19. (-2.35,-1.37] (-1.37,-0.389] (-0.389,0.592]  (0.592,1.57]  (1.57,2.55]
    
20.       7            43              29             13            8

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好象下载过，谢谢了。