[R] mgcv: bam(), error in models with random intercepts and random slopes

Simon Wood simon.wood at bath.edu
Thu Sep 22 15:25:48 CEST 2016

Hi Fotis,

Thanks for the report, and sending me the data and code (off list). The 
problem is triggered by 'ctrial' being a (one column) matrix. An 
immediate fix is

data_a$ctrial <- as.numeric(data_a$ctrial)

- mgcv 1.8-16 will catch the problem automatically internally.


On 20/09/16 17:22, Fotis Fotiadis wrote:
> Hi all
> I am using the bam function of the mgcv package to model behavioral data of
> a learning experiment. To model individual variation in learning rate, I am
> testing models with (a) by-participant random intercepts of trial, (b)
> by-participant random slopes and random intercepts of trial, and (c)
> by-participant random smooth terms.
> While all (a) and (c) models converge, I am getting an error for every
> possible variation of a model with random intercepts and random slopes. For
> example:
> m1.rs<-bam(acc~ 1 + igc + s(ctrial) + s(sbj, bs="re") + s(ctrial, sbj,
> bs="re") , data=data_a, family=binomial)
> Error in G$smooth[[i]]$first.para:G$smooth[[i]]$last.para :
>    argument of length 0
> Any idea on what that error might be?
> Thank you in advance for your time.
> Fotis
> P.S.: R version: 3.3.1, mgcv version: 1.8.15

Simon Wood, School of Mathematics, University of Bristol BS8 1TW UK
+44 (0)117 33 18273     http://www.maths.bris.ac.uk/~sw15190

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