R help - Nov 2012 - Comparing linear regression coefficients to a slope of 1

Hi!

I have a question that is probably very basic, but I cannot figure out how
to do it. I simply need to compare the significance of a regression slope
against a slope of 1, instead of the default of zero.

I know this topic has been posted before, and I have tried to use the
advice given to others to fix my problem. I tried the offset command based
on one of these advice threads as follows:

Regression <- lm(y~x+offset(1*x))

but this resulted in a regression line that was plotted perpendicular to
the data when added with the abline function.

I would be extremely grateful for your help!!

Thanks!!

Cat

	[[alternative HTML version deleted]]

Is this homework?  
 
    PLEASE do read the posting guide 
       http://www.R-project.org/posting-guide.html

albyn

On Sat, Nov 24, 2012 at 07:27:25PM -0500, Catriona Hendry
wrote:
> Hi!
> 
> I have a question that is probably very basic, but I cannot figure out how
> to do it. I simply need to compare the significance of a regression slope
> against a slope of 1, instead of the default of zero.
> 
> I know this topic has been posted before, and I have tried to use the
> advice given to others to fix my problem. I tried the offset command based
> on one of these advice threads as follows:
> 
> Regression <- lm(y~x+offset(1*x))
> 
> but this resulted in a regression line that was plotted perpendicular to
> the data when added with the abline function.
> 
> I would be extremely grateful for your help!!
> 
> Thanks!!
> 
> Cat
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> 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.
> 
-- 
Albyn Jones
Reed College
jones at reed.edu

1. The model is correct :  lm( y~ x + offset(x))
( AFAICS)

2. Read the posting guide, please: Code? I do not know what you mean by:
" this resulted in a regression line that was plotted perpendicular to
the data when added with the abline function."

Of course, maybe someone else will groc this.

3. I wonder if you really want to do what you are doing, anyway. For
example, in comparing two assays to see whether they give "similar"
results, you would **not** do what you are doing. If you care to follow up
on this, I suggest you post complete context to a statistical mailing list,
not here, like stats.stackexchange .com.  Also, feel free to ignore me, of
course. I'm just guessing.

Cheers,
Bert

Cheers,
Bert


On Sat, Nov 24, 2012 at 4:27 PM, Catriona Hendry
<hendry@gwmail.gwu.edu>wrote:
> Hi!
>
> I have a question that is probably very basic, but I cannot figure out how
> to do it. I simply need to compare the significance of a regression slope
> against a slope of 1, instead of the default of zero.
>
> I know this topic has been posted before, and I have tried to use the
> advice given to others to fix my problem. I tried the offset command based
> on one of these advice threads as follows:
>
> Regression <- lm(y~x+offset(1*x))
>
> but this resulted in a regression line that was plotted perpendicular to
> the data when added with the abline function.
>
> I would be extremely grateful for your help!!
>
> Thanks!!
>
> Cat
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@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

	[[alternative HTML version deleted]]

On Nov 24, 2012, at 4:27 PM, Catriona Hendry wrote:
> Hi!
>
> I have a question that is probably very basic, but I cannot figure  
> out how
> to do it. I simply need to compare the significance of a regression  
> slope
> against a slope of 1, instead of the default of zero.
>
> I know this topic has been posted before, and I have tried to use the
> advice given to others to fix my problem. I tried the offset command  
> based
> on one of these advice threads as follows:
>
> Regression <- lm(y~x+offset(1*x))
>
> but this resulted in a regression line that was plotted  
> perpendicular to
> the data when added with the abline function.
>
If the slope were in fact == 1 then what would the offset need to be  
to "correct it" so that it were == 0?

Failing this effort at clapping one hand, then please produce the  
requested dataset and other bits of window dressing requested in the  
Posting Guide, including whether this is a homework problem and what  
your academic institution's expectations are for soliciting help over  
the Internet.

-- 

David Winsemius, MD
Alameda, CA, USA