Creating a table() of counts using a frequency column

Question

I\'ve got data created from the HairEyeColor data

HEC = as.data.frame(HairEyeColor)

which is

Answer 1

We can do it with tapply():

tapply(HEC$Freq, list(ColHair=HEC$Hair,ColEye=HEC$Eye), sum)


  #         ColEye
  # ColHair Brown Blue Hazel Green
  # Black    68   20    15     5
  # Brown   119   84    54    29
  # Red      26   17    14    14
  # Blond     7   94    10    16

---

---

Or using data.table package:

library(data.table)
setDT(HEC)[,list(Freq=sum(Freq)),by=list(Hair, Eye)]

  #     Hair    Eye    Freq
  # 1:  Black   Brown   68
  # 2:  Brown   Brown  119
  # 3:    Red   Brown   26
  # 4:  Blond   Brown    7
  # 5:  Black   Blue    20
  # 6:  Brown   Blue    84
  # 7:    Red   Blue    17
  # 8:  Blond   Blue    94
  # 9:  Black   Hazel   15
  # 10: Brown   Hazel   54
  # 11:   Red   Hazel   14
  # 12: Blond   Hazel   10
  # 13: Black   Green    5
  # 14: Brown   Green   29
  # 15:   Red   Green   14
  # 16: Blond   Green   16

To get it in cross-tab format:

HEC_tab <- dcast(setDT(HEC)[,list(Freq=sum(Freq)),by=list(Hair, Eye)], 
                                         Hair~Eye, value.var = "Freq")

setnames(HEC_tab , c("HairCol/EyeCol", names(HEC_tab)[-1]))

HEC_tab

  #   HairCol/EyeCol Brown Blue Hazel Green
  # 1:         Black    68   20    15     5
  # 2:         Brown   119   84    54    29
  # 3:           Red    26   17    14    14
  # 4:         Blond     7   94    10    16