expcdf<-function(x){1-exp(-x)}

plotexp<-function(xmax,np=1001){
x<-seq(0,xmax,length=np)
lines(x,expcdf(x),type="l",col=3)
}

geomcdfint<-function(k,n){1-(1-1/n)^k}

plotgeom<-function(n,xmax){
x<-(0:(xmax*n))/n
y<-geomcdfint(0:(xmax*n),n)
plot(x,y,type="s",col=2,xlab=paste("n=",n),ylab="")
}

pdf(file="geomconv.pdf",width=8.5,height=11)
par(mfrow=c(4,1),pin=c(6.5,1.6),oma=c(4,0,0,0))
plotgeom(2,4)
plotexp(4)
plotgeom(4,4)
plotexp(4)
plotgeom(8,4)
plotexp(4)
plotgeom(16,4)
plotexp(4)
dev.off()