> ds.mod1 <- aov(weight ~ 1)
> summary(ds.mod1)
             Df Sum Sq Mean Sq F value Pr(>F)
Residuals   239  72592   303.7               
> summary.lm(ds.mod1)

Call:
aov(formula = weight ~ 1)

Residuals:
    Min      1Q  Median      3Q     Max 
-52.767 -11.165  -0.262  10.223  63.603 

Coefficients:
            Estimate Std. Error t value Pr(>|t|)    
(Intercept)  102.437      1.125   91.06   <2e-16 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 17.43 on 239 degrees of freedom

> 
> ds.mod2 <- aov(weight ~ factor(meth))
> summary(ds.mod2)
              Df Sum Sq Mean Sq F value Pr(>F)
factor(meth)   1    338   338.4   1.115  0.292
Residuals    238  72254   303.6               
> summary.lm(ds.mod2)

Call:
aov(formula = weight ~ factor(meth))

Residuals:
    Min      1Q  Median      3Q     Max 
-51.580 -11.461  -0.582   9.969  64.790 

Coefficients:
              Estimate Std. Error t value Pr(>|t|)    
(Intercept)    103.625      1.591  65.150   <2e-16 ***
factor(meth)2   -2.375      2.249  -1.056    0.292    
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 17.42 on 238 degrees of freedom
Multiple R-squared:  0.004662,  Adjusted R-squared:  0.0004797 
F-statistic: 1.115 on 1 and 238 DF,  p-value: 0.2921

> 
> ds.mod3 <- aov(weight ~ factor(trt))
> summary(ds.mod3)
             Df Sum Sq Mean Sq F value   Pr(>F)    
factor(trt)   3   7956  2652.0   9.683 4.73e-06 ***
Residuals   236  64636   273.9                     
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
> summary.lm(ds.mod3)

Call:
aov(formula = weight ~ factor(trt))

Residuals:
   Min     1Q Median     3Q    Max 
-59.16 -10.94   0.78   9.58  57.21 

Coefficients:
             Estimate Std. Error t value Pr(>|t|)    
(Intercept)   106.080      2.137  49.651  < 2e-16 ***
factor(trt)2  -12.410      3.021  -4.107 5.53e-05 ***
factor(trt)3   -4.910      3.021  -1.625    0.105    
factor(trt)4    2.750      3.021   0.910    0.364    
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 16.55 on 236 degrees of freedom
Multiple R-squared:  0.1096,    Adjusted R-squared:  0.09828 
F-statistic: 9.683 on 3 and 236 DF,  p-value: 4.731e-06

> 
> anova(ds.mod1, ds.mod3)
Analysis of Variance Table

Model 1: weight ~ 1
Model 2: weight ~ factor(trt)
  Res.Df   RSS Df Sum of Sq      F    Pr(>F)    
1    239 72592                                  
2    236 64636  3      7956 9.6829 4.731e-06 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
> anova(ds.mod2, ds.mod3)
Analysis of Variance Table

Model 1: weight ~ factor(meth)
Model 2: weight ~ factor(trt)
  Res.Df   RSS Df Sum of Sq      F    Pr(>F)    
1    238 72254                                  
2    236 64636  2    7617.6 13.907 1.953e-06 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1