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• R_回帰分析とbreakpoint へ行く。
  • 1 (2007-10-06 (土) 12:09:08)
  • 2 (2007-10-06 (土) 12:16:27)

R_Baayen

# "1994 年の新聞記事"の中で参照された時代を記録したデータ
head(faz, 3) 
faz$Distance <- 1:nrow(faz)

plot(log(faz$Distance), log(faz$Frequency + 1), 
  xlab = "log Distance", ylab = "log Frequency")

# p.237
faz$LogFrequency <- log(faz$Frequency + 1)
faz$LogDistance <- log(faz$Distance)
breakpoint <- log(59)

faz$ShiftedLogDistance <- faz$LogDistance - breakpoint
plot(faz$ShiftedLogDistance, faz$LogFrequency, 
  xlab = "log Shifted Distance", 
  ylab = "log Frequnecy")

faz.left <- lm(LogFrequency ~ ShiftedLogDistance,
  data = faz[faz$ShiftedLogDistance <= 0,])
faz.right <- lm(LogFrequency ~ ShiftedLogDistance,
  data = faz[faz$ShiftedLogDistance >= 0,])

abline(faz.left, lty = 1)
abline(faz.right, lty = 2)

faz$PastBreakPoint <- as.factor(
  faz$ShiftedLogDistance > 0)
faz.both <- lm(LogFrequency ~ ShiftedLogDistance :
  PastBreakPoint, data = faz)
anova(faz.both, lm(LogFrequency ~ ShiftedLogDistance,
  data = faz))

# p.237
deviances <- rep(0, nrow(faz) - 1)

for(pos in 1:(nrow(faz) - 1)){
 breakpoint <- log(pos)
 faz$ShiftedLogDistance <- 
   faz$LogDistance - breakpoint
 faz$PastBreakPoint <- as.character(
   faz$ShiftedLogDistance > 0)
 faz.both <- lm(LogFrequency ~ 
   ShiftedLogDistance:PastBreakPoint, data = faz)
 deviances[pos] <- deviance(faz.both)
}
# p.239

best <- which(deviances == min(deviances))
best
breakpoint <- log(best)
faz$ShiftedLogDistance <- faz$LogDistance - breakpoint
faz$PastBreakPoint <- as.character(
  faz$ShiftedLogDistance > 0)
faz.both <- lm(LogFrequency ~  
  ShiftedLogDistance:PastBreakPoint, data = faz)

par(mfrow = c(2,2), bg = "white")

plot(log(1:length(deviances)), deviances, type = "l",
  xlab = "breakpoint",ylab = "deviance")
plot( faz$LogDistance, faz$LogFrequency, type = "l",
 xlab = "Log Distance",ylab = "Log Frequency",
 col = "darkgrey")
lines(faz$LogDistance, fitted(faz.both))