From: Tomii <diogenas_at_gmail.com>

Date: Fri, 08 Apr 2011 10:24:45 +0200

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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. Received on Fri 08 Apr 2011 - 08:28:26 GMT

Date: Fri, 08 Apr 2011 10:24:45 +0200

Thank you for your response, but these changes doesn't seem to change anything, outcomes of effect command is still the same - error.

Tomas

On Fri, Apr 1, 2011 at 5:03 AM, John Fox <jfox_at_mcmaster.ca> wrote:

> Dear Tomas,

*>
**> Write the model as
**>
**> mreg01 = lm(enep1 ~ enpres * proximity1), data=a90)
**>
**> That is, it's not necessary to index a90 as a list since it's given as the
**> data argument to lm, and doing so confuses the effect() function. Also,
**> enpres*proximity1 will include both the enpres:proximity1 interaction and
**> enpres + proximity1, which are marginal to the interaction.
**>
**> Next, you must quote the name of the term for which you want to compute
**> effects, thus "enpres:proximity1" in the call to effect().
**>
**> Finally, effect() doesn't compute what are usually termed marginal effects.
**> If you want more information about what it does, see the references given in
**> ?effect.
**>
**> I hope this helps,
**> John
**>
**> ------------------------------------------------
**> John Fox
**> Sen. William McMaster Prof. of Social Statistics
**> Department of Sociology
**> McMaster University
**> Hamilton, Ontario, Canada
**> http://socserv.mcmaster.ca/jfox/
**>
**> On Thu, 31 Mar 2011 22:09:32 +0200
**> Tomii <diogenas_at_gmail.com> wrote:
**> > Hello,
**> >
**> > I try to plot the marginal effect by using package "effects" (example of
**> the
**> > graph i want to get is in the attached picture).
**> > All variables are continuous.
**> >
**> > Here is regression function, results and error effect function gives:
**> >
**> > > mreg01 = lm(a90$enep1 ~ a90$enpres + a90$proximity1 + (a90$enpres *
**> a90$proximity1), data=a90)> summary(mreg01)
**> > Call:
**> > lm(formula = a90$enep1 ~ a90$enpres + a90$proximity1 + (a90$enpres *
**> > a90$proximity1), data = a90)
**> >
**> > Residuals:
**> > Min 1Q Median 3Q Max
**> > -2.3173 -1.3349 -0.5713 0.8938 8.1084
**> >
**> > Coefficients:
**> > Estimate Std. Error t value Pr(>|t|)
**> > (Intercept) 4.2273 0.3090 13.683 < 2e-16 ***
**> > a90$enpres 0.4225 0.2319 1.822 0.072250 .
**> > a90$proximity1 -3.8797 1.0984 -3.532 0.000696 ***
**> > a90$enpres:a90$proximity1 0.8953 0.4101 2.183 0.032025 *
**> > ---
**> > Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
**> >
**> > Residual standard error: 2.029 on 78 degrees of freedom
**> > Multiple R-squared: 0.2128, Adjusted R-squared: 0.1826
**> > F-statistic: 7.031 on 3 and 78 DF, p-value: 0.0003029
**> > > plot(effect(a90$enpres:a90$proximity1, mreg01))Warning messages:1: In
**> a90$enpres:a90$proximity1 :
**> > numerical expression has 82 elements: only the first used2: In
**> > a90$enpres:a90$proximity1 :
**> > numerical expression has 82 elements: only the first used3: In
**> > analyze.model(term, mod, xlevels, default.levels) :
**> > 0 does not appear in the modelError in
**> > plot(effect(a90$enpres:a90$proximity1, mreg01)) :
**> > error in evaluating the argument 'x' in selecting a method for function
**> 'plot'
**> >
**> > >
**> >
**> > Thanks in advance.
**> > Tomas
**>
**>
**>
**>
*

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