R help - Feb 2007 - Convert Class "numeric" to class "lm

Dear R-Users,

 

Background: 

 

I have five multiple imputed datasets. For each datasets I have run a
regression analysis and combined the regression coefficients according to
Rubin (1987) rule. 

 

Problem:

Now I want to use these combined regression coefficients on a different
dataset (with the same variable names but different values) and check how
good they can predict my dependent variable. Normally, it would use the
predict.lm function which requires an object of class "lm". But my
combined
regression coefficients are an object of class "numeric". Therefore, I
need
to know how to convert an object of class "numeric" to a class
"lm".

 

For any suggestion thanks in advance,

 

Simon

 

 

 


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Simon P. Kempf wrote:
> 
> Background: 
> I have five multiple imputed datasets. For each datasets I have run a
> regression analysis and combined the regression coefficients according to
> Rubin (1987) rule. 
> 
So, now you have two numeric values: slope and offset. Right?


Simon P. Kempf wrote:
> 
> Now I want to use these combined regression coefficients on a different
> dataset (with the same variable names but different values) and check how
> good they can predict my dependent variable. Normally, it would use the
> predict.lm function which requires an object of class "lm". But
my
> combined
> regression coefficients are an object of class "numeric".
Therefore, I
> need
> to know how to convert an object of class "numeric" to a class
"lm".
> 
Given numeric values above, I would use multiplication and addition
operations on them and new data.

Try to explore the structure of instances of these classes with str().
You will see that an object of class "lm" is a list with several
components
(12 afair). 
One of them is "coefficients".

You can also construct this object manually from scratch and use
predict.lm(), however, you must correctly create all list elements used by
this function. 
Typing predict.lm in R console will show you the body of this function.
Don't forget to assign the attribute "class".

RSiteSearch("construct lm") will take you here: 
http://finzi.psych.upenn.edu/R/Rhelp02a/archive/32782.html

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