Thank you!

But could you please explain why the 2nd formula is a model to avoid?
Thanks again!
On Tue, Jun 5, 2012 at 6:18 PM, Peter Ehlers <ehlers@ucalgary.ca> wrote:

> You mention 3 models. In all of them, the '-1' simply removes
> the intercept term; help('formula') explains the use of '-'
> in general.
>
> 1. lm(y~ x * w - 1)  is clearly explained in help('formula');
> 2. lm(y~ x:w - 1)   ditto (and this is a model to avoid);
> 3. lm(y~ x/w - 1)   this is equivalent to lm(y~ x + w %in% x - 1)
> where the %in% operator is explained in help('formula'). A good
> and simple example is found in the MASS book (chapter 6) the code
> for which is available in the 'Scripts' subfolder of library/MASS
> of your R installation.
>
> Peter Ehlers
>
>
>
> On 2012-06-05 13:58, Michael wrote:
>
>>  I read your website but still don't know the difference between the
>> three
>> formulas...
>>
>> Thank you!
>>
>> On Mon, Jun 4, 2012 at 11:14 PM, Joshua Wiley<jwiley.psych@gmail.com>**
>> wrote:
>>
>>  Hi Michael,
>>>
>>> This is far from exhaustive (I wrote it as an introduction some years
>>> ago) but you may find it useful to start:
>>> https://joshuawiley.com/R/**formulae_in_R.aspx<https://joshuawiley.com/R/formulae_in_R.aspx>
>>>
>>> Cheers,
>>>
>>> Josh
>>>
>>> On Mon, Jun 4, 2012 at 9:06 PM, Michael<comtech.usa@gmail.com>  wrote:
>>>
>>>> Hi all,
>>>>
>>>> Could you please point me to good materials on various
>>>> tricks/intuitions/techniques of regression, and hopefully in R?
>>>>
>>>> For example, what does lm(y~ x * w - 1) mean vs. lm(y ~ x/w -1 ) vs. lm
>>>>
>>> (y
>>>
>>>> ~ x:w-1), etc...
>>>>
>>>> I just found that even simple linear regression is not that simple and
>>>> there are a lot of tricks/techniques in using them...
>>>>
>>>> Hopefully I can find good materials on these!
>>>>
>>>> Thank you!
>>>>
>>>>        [[alternative HTML version deleted]]
>>>>
>>>> ______________________________**________________
>>>> R-help@r-project.org mailing list
>>>> https://stat.ethz.ch/mailman/**listinfo/r-help<https://stat.ethz.ch/mailman/listinfo/r-help>
>>>> PLEASE do read the posting guide
>>>>
>>> http://www.R-project.org/**posting-guide.html<http://www.r-project.org/posting-guide.html>
>>> <http://www.**r-project.org/posting-guide.**html<http://www.r-project.org/posting-guide.html>>
>>>
>>>
>>> and provide commented, minimal, self-contained, reproducible code.
>>>>
>>>
>>>
>>>
>>> --
>>> Joshua Wiley
>>> Ph.D. Student, Health Psychology
>>> Programmer Analyst II, Statistical Consulting Group
>>> University of California, Los Angeles
>>> https://joshuawiley.com/
>>>
>>>
>>        [[alternative HTML version deleted]]
>>
>> ______________________________**________________
>> R-help@r-project.org mailing list
>> https://stat.ethz.ch/mailman/**listinfo/r-help<https://stat.ethz.ch/mailman/listinfo/r-help>
>> PLEASE do read the posting guide http://www.R-project.org/**
>> posting-guide.html <http://www.r-project.org/posting-guide.html>
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
>

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