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2 data 譴觜 #trees 一危一 伎 蟆碁, 貉朱 覓語 貊蠍 蠏谿朱 覓語襦 覲蟆渚.
df <- trees colnames(df) <- tolower(colnames(df)) head(df) 一危郁 譴觜.
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3 simple regression #襴 覲螳 1螳 蟆曙一 simple regression企手 . lm() 覃 螳 .
lm.out <- lm(volume ~ girth, data=df) summary(lm.out) 蟆郁骸
> summary(lm.out) Call: lm(formula = volume ~ girth, data = df) Residuals: Min 1Q Median 3Q Max -8.065 -3.107 0.152 3.495 9.587 Coefficients: Estimate Std. Error t value Pr(>|t|) (Intercept) -36.9435 3.3651 -10.98 7.62e-12 *** girth 5.0659 0.2474 20.48 < 2e-16 *** --- Signif. codes: 0 *** 0.001 ** 0.01 * 0.05 . 0.1 1 Residual standard error: 4.252 on 29 degrees of freedom Multiple R-squared: 0.9353, Adjusted R-squared: 0.9331 F-statistic: 419.4 on 1 and 29 DF, p-value: < 2.2e-16 蟆郁骸 豕螻焔朱 豕 蟆郁骸襦 螳 蠏 襷 .
volume = 5.0659 * girth - 36.9435
5.0659 螳譴豺螻, -36.9435 覦伎伎る. 願 朱 企慨. 螳れ れ螻 螳.
H(x) = wx + b
豕 讀, cost functioncost(w,b) = avg((H(x) - y)^2) cost.f <- function(par, x, y){ w <- par[1] b <- par[2] H <- w*x + b mean((H - y)^2) } result <- optim(par = c(0, 0), cost.f, x = df$girth, y = df$volume) result 蟆郁骸
> result $par [1] 5.066008 -36.945325 $value [1] 16.91299 $counts function gradient 103 NA $convergence [1] 0 $message NULL 蟆郁骸襯 覲企
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4 multi regression #襴 覲螳 2螳 伎 蟆曙磯ゼ multi regression企手 . multi regression 襷谿螳讌襦 lm() 襯 伎 蟆螻 cost function 襷れ 豕 覦覯 覲伎. 襾殊 lm() 襯 伎覃 れ螻 螳 蟆郁骸襯 詞 .
lm.out <- lm(volume ~ girth + height, data=df) summary(lm.out) 蟆郁骸
> summary(lm.out) Call: lm(formula = volume ~ girth + height, data = df) Residuals: Min 1Q Median 3Q Max -6.4065 -2.6493 -0.2876 2.2003 8.4847 Coefficients: Estimate Std. Error t value Pr(>|t|) (Intercept) -57.9877 8.6382 -6.713 2.75e-07 *** girth 4.7082 0.2643 17.816 < 2e-16 *** height 0.3393 0.1302 2.607 0.0145 * --- Signif. codes: 0 *** 0.001 ** 0.01 * 0.05 . 0.1 1 Residual standard error: 3.882 on 28 degrees of freedom Multiple R-squared: 0.948, Adjusted R-squared: 0.9442 F-statistic: 255 on 2 and 28 DF, p-value: < 2.2e-16 伎 cost function 襷れ伎狩, 覓語 襴暑螳 n螳 蟆 れ螻 螳 hypothesis螳 覲旧″伎る 蟆企.
H(x) = w1x1 + w2x2 + ... + b
願 るる 朱 蠏狩伎狩, 願 襦 豬蠍覃 讌. 讀,
H(X) = WX + b
螳 覓語 W 覓語 X襯 襦 豬蠍 H()襯 襷る simple regression螻 螳 螳 蟆 . b X 貅 蟆
H(X) = WX
螳 襷 . R襦 cost function 襷り鍵 一 b襯 一危一 る, 1襦 誤覃 . b <- 1 tmp <- cbind(b, df) optim() par 朱誤磯 豐蠍郁 譯朱 蟆碁 螻(inner product) る 蠏豺 襷豢一 . 襯 る,
cost.f <- function(par, X, y){ W <- as.matrix(par) X <- as.matrix(X) mean((X%*%W - y)^2) } cost function 燕朱 伎 豕 企慨.
result <- optim(par = c(0, 0, 0), cost.f, X = tmp[1:3], y = tmp[4]) result 蟆郁骸
> result $par [1] -57.9996505 4.7082120 0.3394336 $value [1] 13.61037 $counts function gradient 238 NA $convergence [1] 0 $message NULL 蟆郁骸襯 覲企 lm() 蟇一 .
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5 #れ螻 螳 伎豺螳 一危郁 .
set.seed(123) mydata <- within(data.frame(x=1:10), y <- rnorm(x, mean=x)) mydata$y[2] <- 20 plot(mydata)--豢豌: http://www.alastairsanderson.com/R/tutorials/robust-regression-in-R/ lm() 豕螻焔朱 伎豺 豬渚. lm()襯 磯 れ螻 螳 蟆郁骸襯 視.
lm.out <- lm(y~x, data=mydata) plot(mydata) abline(lm.out, col="red") 豕螻焔 襷螻 るジ 覦覯 企慨襦 . れ螳螻 豢豺 谿伎 螻煙 谿願 覃 磯ゼ 譴讌襷, 蠍一 蠏 ク谿(MAD, mean absolute deviation)襦 磯ゼ 譯殊 襷覲伎.
cost.f <- function(par, x, y){ w <- par[1] b <- par[2] H <- w*x + b mean(abs(H - y)) } result <- optim(par = c(0, 0), cost.f, x = mydata$x, y = mydata$y) result 蟆郁骸
> result $par [1] 0.8849192 0.7047651 $value [1] 2.37167 $counts function gradient 249 NA $convergence [1] 0 $message NULL 蠏碁殊朱 觜蟲企慨.
plot(mydata) abline(lm.out, col="red") abline(a = result$par[1], b = result$par[2], col = "blue") 覘螳 lm() 襯 蟆覲企 蟯谿 覲伎願鹸 . 讌襷, 襷譟煙る曙 .
谿瑚襦 robust regression 蟆郁骸 れ螻 螳. black line rlm() 蟆郁骸. library(MASS) rlm.out <- rlm(y~x, data=mydata) abline(rlm.out) .. 譬. fitting.
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一 覦 蟆 覲企 蟆 . (襴ろ) |