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クロス表の平均

クロス表におけるセル毎の平均を計算

data(warpbreaks)
head(warpbreaks)

##   breaks wool tension
## 1     26    A       L
## 2     30    A       L
## 3     54    A       L
## 4     25    A       L
## 5     70    A       L
## 6     52    A       L

attach(warpbreaks)
brks <- cut(breaks, breaks = c(0, 30, 70))
table(brks, wool)  # クロス表

##          wool
## brks       A  B
##   (0,30]  18 21
##   (30,70]  9  6

n1 <- length(levels(brks))  # 行数
n2 <- length(levels(wool))  # 列数
mlab <- list(brks = levels(brks), wool = levels(wool))  # ラベル
matrix(tapply(breaks, brks:wool, mean), n1, n2, dimnames = mlab)  # セル毎の平均

##          wool
## brks          A     B
##   (0,30]  21.89 49.33
##   (30,70] 21.24 39.33

matrix(tapply(breaks, brks:wool, sd), n1, n2, dimnames = mlab)  # セル毎の標準偏差

##          wool
## brks          A      B
##   (0,30]  6.144 13.096
##   (30,70] 5.567  4.502

detach(warpbreaks)