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
<<attachment: graph.png>>
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