this is my code R of compound option why I could not find function 'pbivnorm' in R ? thats because my R? or what? please help me thanks
#Compound Option
> PoC<-function(Sbtg,St,K1,K2,S,r,t1,t2){
+ D2=((log(St/K2))+((r-(0.5*(S^2)))*(t2/365)))/(S*sqrt(t2/365))
+ D2btg=((log(St/Sbtg))+((r-(0.5*(S^2)))*(t1/365)))/(S*sqrt(t1/365))
+ D1=D2+(S*sqrt(t2/365))
+ D1btg=D2btg+(S*sqrt(t1/365))
+ rho=sqrt(t1/t2)
+ N1=pnorm(-D2btg)
+ N2=pbivnorm(-D2btg,D2,-rho)
+ N3=pbivnorm(-D1btg,D1,-rho)
+ poc=(K2*exp(-r*(t2/365))*N2)-(St*N3)+(K1*exp(-r*(t1/365))*N1)
+ cat(" Valuasi Compound Option Put on Call Saham Facebook ","\n")
+ cat("========================================================================","\n")
+ cat("Harga Pasar Saham AAPL (ST1) = ",St,"\n")
+ cat("Harga Saham Pada saat T1 dan K1 (S*) = ",Sbtg,"\n")
+ cat("Harga Pelaksanaan Compound Option (K1) = ",K1,"\n")
+ cat("Harga Pelaksanaan Opsi Put (K2) = ",K2,"\n")
+ cat("Exercise date pertama (T1) = 28 Maret 2014 ","\n")
+ cat("Exercise date kedua (T2) = 14 Mei 2014 ","\n")
+ cat("Sisa Usia Compound Option = ",t1," hari","\n")
+ cat("Sisa Usia Opsi Put = ",t2," hari","\n")
+ cat("Volatilitas Harga saham = ",S,"\n")
+ cat("Tingkat bunga bebas risiko = ",r,"\n")
+ cat("========================================================================","\n")
+ cat("Harga Compound Option Put on Call = ",poc,"\n")
+ }
> PoC(157.4808243,77.48,77.5,80,0.253941089,0.0025,14,49)
Error in PoC(157.4808243, 77.48, 77.5, 80, 0.253941089, 0.0025, 14, 49) :
could not find function "pbivnorm"
>