By default orthogonal polynomial contrasts are used for ordered
factors. Drop the 'ordered = TRUE' and you will get treatment
contrasts.
hth,
Kingsford Jones
On Tue, Nov 3, 2009 at 8:52 AM, Jen-Chien Chang <jcch...@andrew.cmu.edu> wrote:
> Hi,
>
> I am wondering if there is a way to display the full anme of the regression
> coeffients/factors in the summary?
>
> Suppose I have a bogus data set using weekday as factor which has 7 levels
> such as:
>
> mydata <- sample(364)
> wk <- rep(1:7, 52)
> weekday <-
> factor(wk,1:7,c("Mon","Tue","Wed","Thu","Fri","Sat","Sun"),ordered=T)
> test <- data.frame(mydata,weekday)
> lm.test <- lm(mydata ~ weekday, test)
> summary(lm.test)
> Call:
> lm(formula = mydata ~ weekday)
>
> Residuals:
> Min 1Q Median 3Q Max
> -205.615 -93.486 -2.212 88.851 199.423
>
> Coefficients:
> Estimate Std. Error t value Pr(>|t|)
> (Intercept) 182.5000 5.5137 33.100 <2e-16 ***
> weekday.L -27.0426 14.5878 -1.854 0.0646 .
> weekday.Q -0.9211 14.5878 -0.063 0.9497
> weekday.C -1.6565 14.5878 -0.114 0.9097
> weekday^4 -16.6449 14.5878 -1.141 0.2546
> weekday^5 9.9436 14.5878 0.682 0.4959
> weekday^6 -14.3971 14.5878 -0.987 0.3243
> ---
> Signif. codes: 0 *** 0.001 ** 0.01 * 0.05 . 0.1 1
>
> Residual standard error: 105.2 on 357 degrees of freedom
> Multiple R-squared: 0.01705, Adjusted R-squared: 0.0005341
> F-statistic: 1.032 on 6 and 357 DF, p-value: 0.4039
> -----------------------------------
>
> Why is the name for the regression coeffients/factors display as weekday.L,
> weekday.Q, ....weekday^6 instead of Tue, Wed, and such? Is there a simple
> way of changing options to fix it?
>
> Please advise and many thanks for your help!
>
> Jack Chang
>
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>
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