R help - Oct 2012 - se's and CI's for fitted lines in multivariate regression analysis

I?m entirely stumped on this particular issue and really hoping someone has
some advice for me.
 
I am running a covariant model in lm I would like to give the standard
errors or the confidence intervals for the fitted lines. I?ve been using the
dataset OrangeSprays where I want lines for each level of treatment over the
covariant ?colpos?. I?ve been able to calculate intercepts and slopes for
each lines by adding up the parameters, but this does not make sense when
the comes to the se?s.  I?ve run the summary (model) function, but only get
the differences in standard error between lines. Also by running
confint(model), I have the same problem.

How can I get standard error per or the CI-interval for each fitted line?
I?ve attached the coding underneath.

Thank you,
Sigrid
> data(OrchardSprays)
> model<-lm(decrease~rowpos+colpos+treatment+treatment:colpos)
> summary(model)



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?predict

Have you read An Inrtroduction  to R?

-- Bert

On Wed, Oct 10, 2012 at 6:49 AM, Sigrid <s.stenerud at gmail.com>
wrote:
> I?m entirely stumped on this particular issue and really hoping someone has
> some advice for me.
>
> I am running a covariant model in lm I would like to give the standard
> errors or the confidence intervals for the fitted lines. I?ve been using
the
> dataset OrangeSprays where I want lines for each level of treatment over
the
> covariant ?colpos?. I?ve been able to calculate intercepts and slopes for
> each lines by adding up the parameters, but this does not make sense when
> the comes to the se?s.  I?ve run the summary (model) function, but only get
> the differences in standard error between lines. Also by running
> confint(model), I have the same problem.
>
> How can I get standard error per or the CI-interval for each fitted line?
> I?ve attached the coding underneath.
>
> Thank you,
> Sigrid
>
>> data(OrchardSprays)
>> model<-lm(decrease~rowpos+colpos+treatment+treatment:colpos)
>> summary(model)
>
>
>
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/se-s-and-CI-s-for-fitted-lines-in-multivariate-regression-analysis-tp4645703.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at 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.


-- 

Bert Gunter
Genentech Nonclinical Biostatistics

Internal Contact Info:
Phone: 467-7374
Website:
http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm

Hello,

Your model is equivalent to the model below. As for standard errors, try 
predict.lm with the appropriate argument.

?predict.lm
model <- lm(decrease ~ rowpos + colpos*treatment, data = OrchardSprays)
predict(model, se.fit = TRUE, interval = "confidence")

Hope this helps,

Rui Barradas
Em 10-10-2012 14:49, Sigrid escreveu:
> I?m entirely stumped on this particular issue and really hoping someone has
> some advice for me.
>   
> I am running a covariant model in lm I would like to give the standard
> errors or the confidence intervals for the fitted lines. I?ve been using
the
> dataset OrangeSprays where I want lines for each level of treatment over
the
> covariant ?colpos?. I?ve been able to calculate intercepts and slopes for
> each lines by adding up the parameters, but this does not make sense when
> the comes to the se?s.  I?ve run the summary (model) function, but only get
> the differences in standard error between lines. Also by running
> confint(model), I have the same problem.
>
> How can I get standard error per or the CI-interval for each fitted line?
> I?ve attached the coding underneath.
>
> Thank you,
> Sigrid
>
>> data(OrchardSprays)
>> model<-lm(decrease~rowpos+colpos+treatment+treatment:colpos)
>> summary(model)
>
>
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/se-s-and-CI-s-for-fitted-lines-in-multivariate-regression-analysis-tp4645703.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at 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.