[R] Difference between summary.lm() and summary.aov()

[Spencer Graves]

      The square of a Student's t with "df" degrees of freedom is an F 
distribution with 1 and "df" degrees of freedom. 
     
      hope this helps.  spencer graves

Alexander Sirotkin [at Yahoo] wrote:

>I have a simple linear model (fitted with lm()) with 2
>independant
>variables : one categorical and one integer.
>
>When I run summary.lm() on this model, I get a
>standard linear
>regression summary (in which one categorical variable
>has to be
>converted into many indicator variables) which looks
>like :
>
>            Estimate Std. Error t value Pr(>|t|)
>(Intercept)  -3595.3     2767.1  -1.299   0.2005
>physicianB     802.0     2289.5   0.350   0.7277
>physicianC    4906.8     2419.8   2.028   0.0485 *
>severity      7554.4      906.3   8.336 1.12e-10 ***
>
>and when I run summary.aov() I get similar ANOVA table
>: 
>
>           Df     Sum Sq    Mean Sq F value    Pr(>F)
>physician    2  294559803  147279901  3.3557   0.04381
>*
>severity     1 3049694210 3049694210 69.4864 1.124e-10
>***
>Residuals   45 1975007569   43889057
>
>What is absolutely unclear to me is how F-value and
>Pr(>F) for the
>categorical "physician" variable of the summary.aov()
>is calculated
>from the t-value of the summary.lm() table.
>
>I looked at the summary.aov() source code but still
>could not figure
>it.
>
>Thanks a lot.
>
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