## 原文链接： http://tecdat.cn/?p=21557

```> summary(reg)
Call:
Residuals:
Min      1Q  Median      3Q     Max
-29.069  -9.525  -2.272   9.215  43.201
Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept) -17.5791     6.7584  -2.601   0.0123 *
speed         3.9324     0.4155   9.464 1.49e-12 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
Residual standard error: 15.38 on 48 degrees of freedom
Multiple R-squared:  0.6511,    Adjusted R-squared:  0.6438
F-statistic: 89.57 on 1 and 48 DF,  p-value: 1.49e-12```

```for(x in seq(3,30)){
+ Yx=b0+b1*x
+ V=vcov(reg)
+ IC1=Yx+c(-1,+1)*1.96*sqrt(Vx)
+ s=summary(reg)\$sigma
+ IC2=Yx+c(-1,+1)*1.96*s```

`lm(dist~speed,data=cars[I,])`

```Residuals:
Min      1Q  Median      3Q     Max
-23.529  -7.998  -5.394  11.634  39.348
Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept) -20.7408     9.4639  -2.192   0.0418 *
speed         4.2247     0.6129   6.893 1.91e-06 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
Residual standard error: 16.62 on 18 degrees of freedom
Multiple R-squared:  0.7252,    Adjusted R-squared:   0.71
F-statistic: 47.51 on 1 and 18 DF,  p-value: 1.91e-06
> for(x in seq(3,30,by=.25)){
+   Yx=b0+b1*x
+   V=vcov(reg)
+   IC=Yx+c(-1,+1)*1.96*sqrt(Vx)
+   points(x,Yx,pch=19```

```fit      lwr       upr
1 42.62976 34.75450  50.50502
2 84.87677 68.92746 100.82607
> predict(reg,
fit      lwr      upr
1 42.62976 6.836077 78.42344```

```> image(VX2,VX3,VY)

`> persp(VX2,VX3,VY,ticktype=detailed)`

`> abline(reg1)`

`lm(sqrt(dist)~speed,data=cars)`

```Residuals:
Min      1Q  Median      3Q     Max
-29.472  -9.559  -2.088   7.456  44.412
Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept)      -17.2964     6.7709  -2.555   0.0139 *
speed              4.3140     0.5762   7.487  1.5e-09 ***
speed > s TRUE  -7.5116     7.8511  -0.957   0.3436
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
Residual standard error: 15.39 on 47 degrees of freedom
Multiple R-squared:  0.6577,    Adjusted R-squared:  0.6432
F-statistic: 45.16 on 2 and 47 DF,  p-value: 1.141e-11```

```Residuals:
Min      1Q  Median      3Q     Max
-29.502  -9.513  -2.413   5.195  45.391
Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept)          -7.6519    10.6254  -0.720  0.47500
speed                 3.0186     0.8627   3.499  0.00103 **
speed - s  1.7562     1.4551   1.207  0.23350
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
Residual standard error: 15.31 on 47 degrees of freedom
Multiple R-squared:  0.6616,    Adjusted R-squared:  0.6472
F-statistic: 45.94 on 2 and 47 DF,  p-value: 8.761e-12```

```posi=function(x) ifelse(x>0,x,0)

Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept)           -7.6305    16.2941  -0.468   0.6418
speed                  3.0630     1.8238   1.679   0.0998 .
positive(speed - s1)   0.2087     2.2453   0.093   0.9263
positive(speed - s2)   4.2812     2.2843   1.874   0.0673 .
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
Residual standard error: 15 on 46 degrees of freedom
Multiple R-squared:  0.6821,    Adjusted R-squared:  0.6613
F-statistic: 32.89 on 3 and 46 DF,  p-value: 1.643e-11```