[R] Question about linear regression in R

[David Winsemius]

On Nov 14, 2011, at 10:49 PM, Miles Yang wrote:

> Hi all,
> I wrote a r program as below:
>
> x <- 1:10
> y <- c(3,3,3,3,3,3,3,3,3,3)
>
> fit <- lm(log(y) ~ x)
> summary(fit)
>
> And I expect to get some error message from R, because "y" is  
> constant.
> But, I got the message as below:

You are asking R to tell you if the mean of the log of 3 was different  
than 0. It is.

-- 
David.
>
>> summary(fit)
>
> Call:
> lm(formula = log(y) ~ x)
>
> Residuals:
>       Min         1Q     Median         3Q        Max
> -6.802e-17 -3.933e-17 -1.063e-17  1.807e-17  1.530e-16
>
> Coefficients:
>              Estimate Std. Error    t value Pr(>|t|)
> (Intercept)  1.099e+00  4.569e-17  2.404e+16   <2e-16 ***
> x           -1.275e-17  7.364e-18 -1.732e+00    0.122
> ---
> Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
>
> Residual standard error: 6.688e-17 on 8 degrees of freedom
> Multiple R-squared: 0.5794, Adjusted R-squared: 0.5269
> F-statistic: 11.02 on 1 and 8 DF,  p-value: 0.01054
>
> How could this be possible?
> Did I missing something in my R code?
>
> Best,
> Miles
> -- 
> －－－－－－－－－－－－－－－－－－
> Miles Yang
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> E-mail：miles2yang at gmail.com
> －－－－－－－－－－－－－－－－－－
>
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David Winsemius, MD
West Hartford, CT