specifying model with multiple interactions
Hi James, I think you probably want something along the lines of BatUp ~ Speed + Delivery + (1|Subject) + (0+Speed|Subject) + (0+Delivery|Subject) assuming that Subject is a unique identifier for each participant. I highly doubt that you want the (1|Delivery) term in there, as it surely makes more sense to think of this as a fixed factor. I'm sure someone will correct me if I'm wrong... -Ista
On Mon, Mar 1, 2010 at 5:47 PM, James Croft <james.croft at aut.ac.nz> wrote:
I am having trouble specifying a mixed effects model and would appreciate some guidance. Background We are interested in how cricket batsmen respond to balls delivered from bowling machines. We filmed batsmen facing deliveries at different speeds from a bower and machine. The data is very expensive because each video has to be digitized by hand to identify various parameters of interest. Hence we only have data on 13 subjects (and it has missing values). One objective is to predict the timing of bat lift (BatUp) by delivery speed (Speed) for a given condition (Delivery) and to assess the variability across subjects (Subject). Delivery ?: Factor w/ 2 levels "Bowler","Machine" Subject ? : Factor w/ 13 levels Speed ? ? : num BatUp ? ? : num So I believe I want to predict a fixed effect for speed and random slope and intercept for each level of a factor created by Subject:Delivery I'm getting a bit confused with the combinations of random effect. I have read through a few of the chapters ?of Doug Bates. (2010). lme4: Mixed-effects modeling with R. This is as far as I have got... BatUp ~ Speed + (1|Delivery) + (1|Subject) + (1|Subject:Delivery) + (0+Speed|Subject:Delivery) Thanks in advance for any help. Regards, James Regards, James
________________________________________ James Croft, PhD Research Fellow Sport Performance Research Institute New Zealand School of Sport and Recreation AUT University Private Bag 92006 Auckland 1142 New Zealand Phone 64-9-921 9999 ext 7685 Fax 64-9 921 9960 Email james.croft at aut.ac.nz http://www.isrrnz.ac.nz/ _______________________________________________ R-sig-mixed-models at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models
Ista Zahn Graduate student University of Rochester Department of Clinical and Social Psychology http://yourpsyche.org