R 如何使用lm()检索三维拟合方程?
假设我有以下代码来拟合双曲抛物线:R 如何使用lm()检索三维拟合方程?,r,lm,polynomials,R,Lm,Polynomials,假设我有以下代码来拟合双曲抛物线: # attach(mtcars) hp_fit <- lm(mpg ~ poly(wt, disp, degree = 2), data = mtcars) 我不明白如何解释(Intercept)列下poly()右侧的变化数字。这些数字的意义是什么?我将如何从总结中构建双曲抛物面拟合方程?当您进行比较时 with(mtcars, poly(wt, disp, degree=2)) with(mtcars, poly(wt, degree=2))
# attach(mtcars)
hp_fit <- lm(mpg ~ poly(wt, disp, degree = 2), data = mtcars)
我不明白如何解释(Intercept)
列下poly()
右侧的变化数字。这些数字的意义是什么?我将如何从总结中构建双曲抛物面拟合方程?当您进行比较时
with(mtcars, poly(wt, disp, degree=2))
with(mtcars, poly(wt, degree=2))
with(mtcars, poly(disp, degree=2))
1.0
2.0
指的是wt
的第一级和第二级,0.1
0.2
指的是disp
的第一级和第二级。1.1
是一个交互术语。您可以通过比较来检查:
summary(lm(mpg ~ poly(wt, disp, degree=2, raw=T), data=mtcars))$coe
# Estimate Std. Error t value Pr(>|t|)
# (Intercept) 4.692786e+01 7.008139762 6.6961935 4.188891e-07
# poly(wt, disp, degree=2, raw=T)1.0 -1.062827e+01 8.311169003 -1.2787937 2.122666e-01
# poly(wt, disp, degree=2, raw=T)2.0 2.079131e+00 2.333864211 0.8908534 3.811778e-01
# poly(wt, disp, degree=2, raw=T)0.1 -3.172401e-02 0.060528241 -0.5241191 6.046355e-01
# poly(wt, disp, degree=2, raw=T)1.1 -2.660633e-02 0.032228884 -0.8255431 4.165742e-01
# poly(wt, disp, degree=2, raw=T)0.2 2.019044e-04 0.000135449 1.4906301 1.480918e-01
summary(lm(mpg ~ wt*disp + I(wt^2) + I(disp^2) , data=mtcars))$coe[c(1:2, 4:3, 6:5), ]
# Estimate Std. Error t value Pr(>|t|)
# (Intercept) 4.692786e+01 7.008139762 6.6961935 4.188891e-07
# wt -1.062827e+01 8.311169003 -1.2787937 2.122666e-01
# I(wt^2) 2.079131e+00 2.333864211 0.8908534 3.811778e-01
# disp -3.172401e-02 0.060528241 -0.5241191 6.046355e-01
# wt:disp -2.660633e-02 0.032228884 -0.8255431 4.165742e-01
# I(disp^2) 2.019044e-04 0.000135449 1.4906301 1.480918e-01
这会产生相同的值。请注意,我使用了
raw=TRUE
进行比较。如果您通过在poly()内部设置raw=TRUE
来使用原始多项式,这不会太难。使用正交多项式更有利于回归的稳定性,但方程的提取要困难得多。相关阅读是和。
summary(lm(mpg ~ poly(wt, disp, degree=2, raw=T), data=mtcars))$coe
# Estimate Std. Error t value Pr(>|t|)
# (Intercept) 4.692786e+01 7.008139762 6.6961935 4.188891e-07
# poly(wt, disp, degree=2, raw=T)1.0 -1.062827e+01 8.311169003 -1.2787937 2.122666e-01
# poly(wt, disp, degree=2, raw=T)2.0 2.079131e+00 2.333864211 0.8908534 3.811778e-01
# poly(wt, disp, degree=2, raw=T)0.1 -3.172401e-02 0.060528241 -0.5241191 6.046355e-01
# poly(wt, disp, degree=2, raw=T)1.1 -2.660633e-02 0.032228884 -0.8255431 4.165742e-01
# poly(wt, disp, degree=2, raw=T)0.2 2.019044e-04 0.000135449 1.4906301 1.480918e-01
summary(lm(mpg ~ wt*disp + I(wt^2) + I(disp^2) , data=mtcars))$coe[c(1:2, 4:3, 6:5), ]
# Estimate Std. Error t value Pr(>|t|)
# (Intercept) 4.692786e+01 7.008139762 6.6961935 4.188891e-07
# wt -1.062827e+01 8.311169003 -1.2787937 2.122666e-01
# I(wt^2) 2.079131e+00 2.333864211 0.8908534 3.811778e-01
# disp -3.172401e-02 0.060528241 -0.5241191 6.046355e-01
# wt:disp -2.660633e-02 0.032228884 -0.8255431 4.165742e-01
# I(disp^2) 2.019044e-04 0.000135449 1.4906301 1.480918e-01