[R] what is the intercept of a two-way anova model without interaction term?

[Xiaokuan Wei]

Dear list,

I have a question regarding the meaning of intercept term in a two-way anova 
model without interaction term.

for example (let's assume there is no interaction between factor1 and factor2) :

> df
        val        factor1 factor2
1  48.61533       A      t1
2 171.13535       B      t1
3  65.96884       C      t1
4  63.71222       A      t2
5  80.22049       B      t2
6  96.95929       C      t2
7  38.70078       A      t3
8  99.44787       B      t3
9  36.58818       C      t3

the summary of regression :

> summary(m)
Call:
lm(formula = val ~ factor1 + factor2, data = df)
Residuals:
      1       2       3       4       
5       6       7       8       9 
-19.040  36.889 -17.849  11.000 -39.084  28.084   8.040   2.195 -10.235 
Coefficients:
            Estimate Std. Error t value Pr(>|t|)  
(Intercept)    67.66      25.42   2.661   0.0563 .
factor1B       66.59      27.85   2.391   0.0751 .
factor1C       16.16      27.85   0.580   0.5928  
factor2t2     -14.94      27.85  -0.537   0.6200  
factor2t3     -36.99      27.85  -1.328   0.2548  
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ 
’ 1 
Residual standard error: 34.11 on 4 degrees of freedom
Multiple R-squared: 0.6669,     Adjusted R-squared: 0.3338 
F-statistic: 2.002 on 4 and 4 DF,  p-value: 0.2589 


This is contrast treatment, and my question is what the intercept (here is 
67.66) represent for?

Thank you.


Xiaokuan


      
        [[alternative HTML version deleted]]


______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.