# R commands that show a Gibbes sampler constructed from 
# conditional densities with no proper joint density will
# not converge
x=NULL
y=NULL
xi=rexp(1)
yi=rexp(1)
for (i in 1:1000){
x[i]=rexp(1,yi)
xi=x[i]
y[i]=rexp(1,xi)
yi=y[i]
}
par(mfrow=c(2,2))
plot(x)
hist(x[101:1000])
plot(y)
hist(y[101:1000])
#Adjust plotting parameters
xq3=quantile(x,.75)
yq3=quantile(y,.75)
plot(x,ylim=c(0,xq3))
hist(x[x<50])
plot(y,ylim=c(0,yq3))
hist(y[y<50])
#Changing scale
plot(log(x))
hist(log(x))
plot(log(y))
hist(log(y))