[R] Simple question about formulae in R!?

[R. Michael Weylandt]

On Fri, Aug 10, 2012 at 7:36 AM, ONKELINX, Thierry
<Thierry.ONKELINX at inbo.be> wrote:
> Dear Johan,
>
> Why should it be complicated? You have a very simple model, thus a very simple formula. Isn't that great?
>
> Your formula matches the model. Though Trust~Culture + Structure * Speed_of_Integration is another option. The model fit is the same, the only difference is the parameterization of the model.

Note quite, I don't think: A*B is shorthand for A + B + A:B where A:B
is the 2nd order (interaction) term. The OP only had the 2nd order
term without the main effects.

OP: You almost certainly want A*B -- it's strange (though certainly
not impossible) to have good models where you only have interactions
but not main effects.

Cheers,
Michael


>
> Best regards,
>
> Thierry
>
> ir. Thierry Onkelinx
> Instituut voor natuur- en bosonderzoek / Research Institute for Nature and Forest
> team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
> Kliniekstraat 25
> 1070 Anderlecht
> Belgium
> + 32 2 525 02 51
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>
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>
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>
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>
>
> -----Oorspronkelijk bericht-----
> Van: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] Namens Johan Haasnoot
> Verzonden: vrijdag 10 augustus 2012 9:15
> Aan: r-help at r-project.org
> Onderwerp: [R] Simple question about formulae in R!?
>
> Good morning reader,
>
>
>
> I have encountered a, probably, simple issue with respect to the *formulae* of a *regression model* I want to use in my research. I'm researching alliances as part of my study Business Economics (focus Strategy) at the Vrije Universiteit in Amsterdam. In the research model I use a moderating variable, I'm looking for confirmation or help on the formulation of the model.
>
>
>
> The research model consist of 2 explanatory variables, a moderating variable and 1 response variable. The first explanatory variable is Culture, measured on a nominal scale and the second is Structure of the alliance, also measured on a nominal scale. The moderating variable in the relation towards Trust is Speed of Integration, measured as an interval.
> The response variable is Trust, measured on a nominal scale (highly likely a 5-point Likert scale). Given the research model and the measurement scales, I intent to use a ordered probit model, often used in Marketing models,  to execute the regression modelling. I can't seem to find confirmation on how to model the formulae. I have been reading and studying R! for a couple of weeks now, read a lot of books from the R! series in the past, but I can't get a grasp on this seemingly simple formulae. I think I understand how to model multinomial regression (using the R-package MNP), how to execute a Principal Components Analysis and an Explanatory Factor analysis (obviously I'm using a questionnaire to collect my data), but the formulae itself seems to be to simple.
>
>
>
> I expect to use the interaction symbol: "Trust~Culture + Structure :
> Speed_of_Integration" for the formulae, but is it really this simple? Can anybody confirm this or help me, advise me on this issue?
>
>
> Kind regards,
>
> --
>
> Met vriendelijke groet,
>
> Johan Haasnoot
>
> De Haan & Martojo
> Kerklaan 5
> 3645 ES Vinkeveen
> Telefoon: 0297-266354
> Mobiel: 06-81827665
> Email: johan.haasnoot at dh-m.nl
> Website: www.dehaanenmartojo.nl
>
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