R Under development (unstable) (2024-09-21 r87186 ucrt) -- "Unsuffered Consequences"
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> # test the t distribution
> 
> library(glmm)
Loading required package: trust
Loading required package: mvtnorm
Loading required package: Matrix
Loading required package: parallel
Loading required package: doParallel
Loading required package: foreach
Loading required package: iterators
> 
> tdist2<-function(tconst,u, Dstarinv,zeta,myq){
+ 	inside<-1+t(u)%*%Dstarinv%*%u/zeta
+ 	logft<-tconst - ((zeta+myq)/2)*log(inside)
+ 	as.vector(logft)
+ }
> 
> zeta<-5
> myq<-10
> set.seed(1234)
> u<-rt(10,df=zeta)
> Dstarinvdiag<-rep(1.1,10)
> tconstant<-glmm:::tconstant
> tconst<-tconstant(zeta,myq,Dstarinvdiag)
> 
> Dstarinv<-diag(Dstarinvdiag)
> tR<-tdist2(tconst,u,Dstarinv,zeta,myq)
> 
> #compare version in R to version in C
> tC<-.C(glmm:::C_tdist,as.double(Dstarinv),  as.integer(myq), as.double(u), as.integer(zeta), as.double(tconst), double(1))
> all.equal(tC[[6]],tR)
[1] TRUE
> 
> #compare my version to the mvtnorm version
> Dstar<-diag(10)/1.1
> theirs<-dmvt(u,sigma=Dstar,df=zeta)
> theirs==tR
[1] TRUE
> 
> proc.time()
   user  system elapsed 
   1.20    0.28    1.48