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

[Bert Gunter]

I would have thought the first place to look would be ?interaction.plot

Cheers,

Bert
Bert Gunter

"Data is not information. Information is not knowledge. And knowledge
is certainly not wisdom."
   -- Clifford Stoll


On Sun, Nov 22, 2015 at 2:44 PM, angelo.arcadi at virgilio.it
<angelo.arcadi at virgilio.it> wrote:
> 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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