R help - Jun 2006 - Extract information from the summary of 'lm'

Hi Everyone, 

I just don't know how to extract the information I
want from the summary of a linear regression model
fitting. 

For example, I fit the following simple linear
regression model: 

results = lm(y_var ~ x_var)

summary(results) gives me:

Call:
lm(formula = y_var ~ x_var)

Residuals:
    Min      1Q  Median      3Q     Max 
-5.9859 -1.5849  0.4574  2.0163  4.6015 

Coefficients:
            Estimate Std. Error t value Pr(>|t|)    
(Intercept)  -1.7782     0.5948  -2.990 0.004879 ** 
x_var         2.1237     0.5073   4.187 0.000162 ***
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05
'.'
0.1 ' ' 1 


I can get the esitmates (i.e. -1.7782 and 2.1237) of
coefficients by calling

results$coefficients

But I don't know how to get the corresponding t values
and P values for those coefficients. I am running a
lot of regression models and I can not run 'summary'
every time to get the t and P values for each model.

Can anybody give me some hints? Thank you very much!

Best,

Jun

----------------------------
Jun Ding, Ph.D. student
Department of Biostatistics
University of Michigan
Ann Arbor, MI, 48105

>   ctl <- c(4.17,5.58,5.18,6.11,4.50,4.61,5.17,4.53,5.33,5.14)
>      trt <- c(4.81,4.17,4.41,3.59,5.87,3.83,6.03,4.89,4.32,4.69)
>      group <- gl(2,10,20, labels=c("Ctl","Trt"))
>      weight <- c(ctl, trt)
> lm.D9 <- lm(weight ~ group)
> summary(lm.D9)$coef
            Estimate Std. Error   t value     Pr(>|t|)
(Intercept)    5.032  0.2202177 22.850117 9.547128e-15
groupTrt      -0.371  0.3114349 -1.191260 2.490232e-01
> class(summary(lm.D9)$coef)
[1] "matrix"

 > colnames(summary(lm.D9)$coef)
[1] "Estimate"   "Std. Error" "t value"   
"Pr(>|t|)"

So you can get t and p-value  by
 >summary(lm.D9)$coef[,"t value"]
> summary(lm.D9)$coef[,"Pr(>|t|)"]
If you want to get the result as matrix,just use the drop=F
argument.
> summary(lm.D9)$coef[,"Pr(>|t|)",drop=F]
                Pr(>|t|)
(Intercept) 9.547128e-15
groupTrt    2.490232e-01



2006/6/21, Jun Ding <dingjun_cn at yahoo.com>:
> Hi Everyone,
>
> I just don't know how to extract the information I
> want from the summary of a linear regression model
> fitting.
>
> For example, I fit the following simple linear
> regression model:
>
> results = lm(y_var ~ x_var)
>
> summary(results) gives me:
>
> Call:
> lm(formula = y_var ~ x_var)
>
> Residuals:
>     Min      1Q  Median      3Q     Max
> -5.9859 -1.5849  0.4574  2.0163  4.6015
>
> Coefficients:
>             Estimate Std. Error t value Pr(>|t|)
> (Intercept)  -1.7782     0.5948  -2.990 0.004879 **
> x_var         2.1237     0.5073   4.187 0.000162 ***
> ---
> Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05
'.'
> 0.1 ' ' 1
>
>
> I can get the esitmates (i.e. -1.7782 and 2.1237) of
> coefficients by calling
>
> results$coefficients
I think using coef(result) is a better habit.
> But I don't know how to get the corresponding t values
> and P values for those coefficients. I am running a
> lot of regression models and I can not run 'summary'
> every time to get the t and P values for each model.
>
> Can anybody give me some hints? Thank you very much!
>
> Best,
>
> Jun
>
> ----------------------------
> Jun Ding, Ph.D. student
> Department of Biostatistics
> University of Michigan
> Ann Arbor, MI, 48105
>
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http://www.R-project.org/posting-guide.html
>

-- 
??????
Department of Sociology
Fudan University