[R] (no subject)

[allan_sta_staff_sci_main_uct@mail.uct.ac.za]

hi all

why does the following not work???

this was someone elses code and i couldnt explain why it doesn't work.

m=matrix(c(0,0),2,1)
v=matrix(c(1,0,0,1),2,2)

Y=function(X1,X2,mu=m,V=v)
{
	X=matrix(c(X1,X2),2,1)
	a=(1/((2*pi)*sqrt(det(V))))*exp((-0.5)*(t(X-mu)%*%solve(V)%*%(X-mu)))
	a[1]
}

x1=seq(-1,1)
x2=x1

Z=outer(x1,x2,FUN="Y",mu=m,V=v)

persp(x1,x2,Z)




my code:

BINORMAL<-function(varx=1,vary=1,covxy=0,meanx=0,meany=0)
{
	#the following function plots the density of a bi variate normal distribution

	covXY<-matrix(c(varx,covxy,covxy,vary),2,2)
	A<-solve(covXY)

	#up<-max(meanx+4*varx^.5,meanx-4*varx^.5,meany+4*vary^.5,meany-4*vary^.5)
	#x <- seq(-up,up,length=50)
	#y <- x

	x <- seq(meanx-3*varx^.5,meanx+3*varx^.5,length=50)
	y <- seq(meany-3*vary^.5,meany+3*vary^.5,length=50)

	f <- function(x,y,...)
	{
		detA<-det(A)
		quadForm<-A[1,1]*(x-meanx)^2+2*A[1,2]*(x-meanx)*(y-meany)+A[2,2]*(y-meany)^2
		K<-sqrt(detA)/(2*pi)
		exp(-0.5*quadForm)*K
	}

	z <- outer(x, y, f)

	par(mfrow=c(1,2))
	persp(x, y, z,theta = 30, phi = 30,col="white",main="BI-VARIATE NORMAL
DISTRIBUTION")
	contour(x,y,z,main=paste("xy plot, corr(X,Y)= ",(covxy/(varx*vary)^.5)))

	print("NOTE -sqrt(varx*vary)<=covxy<=sqrt(varx*vary)")
	#print(A)
}
BINORMAL(varx=1,vary=1,covxy=0,meanx=0,meany=0)

thanx

/allan