# [R] (no subject)

Date: Wed 05 Oct 2005 - 23:31:52 EST

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)
K<-sqrt(detA)/(2*pi)
}

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

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