多列聯繫表

• table()生成多維列表

> mytable <- xtabs(~ Treatment+Sex+Improved, data=Arthritis)  
> mytable
, , Improved = None

         Sex
Treatment Female Male
  Placebo     19   10
  Treated      6    7

, , Improved = Some

         Sex
Treatment Female Male
  Placebo      7    0
  Treated      5    2

, , Improved = Marked

         Sex
Treatment Female Male
  Placebo      6    1
  Treated     16    5

• ftable()

生成一種緊湊而吸引人的方式輸出多維列聯表

> ftable(mytable)    #將mytable做爲參數傳入fatable()
                 Improved None Some Marked
Treatment Sex                             
Placebo   Female            19    7      6
          Male              10    0      1
Treated   Female             6    5     16
          Male               7    2      5

 

• 邊際及比例計算

> margin.table(mytable, 1)    #計算第一個變量 Treatment的邊際頻數（即求個數和）
Treatment
Placebo Treated 
     43      41 
> margin.table(mytable, 2)
Sex
Female   Male 
    59     25 
> margin.table(mytable, 2)
Sex
Female   Male 
    59     25 
> margin.table(mytable, c(1,3))  # 計算Treatment*Improved分組的邊際頻數
         Improved
Treatment None Some Marked
  Placebo   29    7      7
  Treated   13    7     21
> ftable(prop.table(mytable, c(1,2)))  #計算Treatment*Sex組合中改善狀況爲None，Some和Marked的比例
                 Improved       None       Some     Marked
Treatment Sex                                             
Placebo   Female          0.59375000 0.21875000 0.18750000
          Male            0.90909091 0.00000000 0.09090909
Treated   Female          0.22222222 0.18518519 0.59259259
          Male            0.50000000 0.14285714 0.35714286
> ftable(addmargins(prop.table(mytable, c(1, 2)), 3))  #乘以100，獲得百分比而不是比例
                 Improved       None       Some     Marked        Sum
Treatment Sex                                                        
Placebo   Female          0.59375000 0.21875000 0.18750000 1.00000000
          Male            0.90909091 0.00000000 0.09090909 1.00000000
Treated   Female          0.22222222 0.18518519 0.59259259 1.00000000
          Male            0.50000000 0.14285714 0.35714286 1.00000000