[R] How to plot results from lme in presence of a significant interaction

[Fox, John]

Dear Angelo,

You might try the Effect() function in the effects package: plot(Effect(c("Weight", "Height"), lme_Centroid)) .

I hope this helps,
 John

-----------------------------
John Fox, Professor
McMaster University
Hamilton, Ontario
Canada L8S 4M4
Web: socserv.mcmaster.ca/jfox



> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of
> angelo.arcadi at virgilio.it
> Sent: November 22, 2015 5:44 PM
> To: r-help at r-project.org
> Subject: [R] How to plot results from lme in presence of a significant interaction
> 
> Dear list members,
> I wonder which is the best way to plot in r the results from the lme function, in
> presence of a significant interaction.
>  My model has two interacting fixed effects and a random effect. The analysis is
> from an experiment where 19 participants had to adjust the Centroid
> parameter of some sounds stimuli, and I want to assess whether  there is a
> relationship between their choices and their height and weight. There were 12
> stimuli repeated twice for a total of 24 trials.
> Here is the output of my analysis:
> 
>     > library(nlme)
>     > lme_Centroid <- lme(Centroid ~ Weight*Height, data = scrd, random = ~1 |
> Subject)
>     >
>     > summary(lme_Centroid)
>     Linear mixed-effects model fit by REML
>      Data: scrd
>            AIC      BIC    logLik
>       25809.38 25840.69 -12898.69
> 
>     Random effects:
>      Formula: ~1 | Subject
>             (Intercept) Residual
>     StdDev:    398.9658  3027.67
> 
>     Fixed effects: Centroid ~ Weight * Height
>                        Value Std.Error   DF   t-value p-value
>     (Intercept)   -20232.203  9101.096 1349 -2.223051  0.0264
>     Weight           478.854   152.184   15  3.146536  0.0067
>     Height           140.440    52.194   15  2.690751  0.0168
>     Weight:Height     -2.725     0.838   15 -3.253770  0.0053
>      Correlation:
>                   (Intr) Weight Height
>     Weight        -0.927
>     Height        -0.994  0.886
>     Weight:Height  0.951 -0.996 -0.919
> 
>     Standardized Within-Group Residuals:
>            Min         Q1        Med         Q3        Max
>     -1.5059828 -0.8664208 -0.2111113  0.7098706  2.3620633
> 
>     Number of Observations: 1368
>     Number of Groups: 19
> 
> 
> 
> I
>  do not know how to represent in R these results. I tried xyplot(Centroid ~
> Weight * Height, type = c("p","r"), data = scrd) but I  guess it is wrong.
> 
> Thank you in advance
> 
> Best regards
> 
> Angelo
> 	[[alternative HTML version deleted]]
> 
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