ksppgram<- function(n,np,nv,a,b){
	#	n=number of observations
	#	np=number of periods of cyclical component
	#	nv=noise variance
	#	a=coefficient of cosine term
	#	b=coefficient of sine term
	kt<-seq(1,n)
	f<-2*pi*np*(kt-1)/n

	# look at cosine term
	z<-a*cos(f)
	par(mfrow=c(2,2))
	tsplot(z)

	# add in sin term
	z<-z+b*sin(f)
	tsplot(z)

	# add noise
	z<-z+rnorm(n,0,nv)
	tsplot(z)

	# plot periodogram
	spec.pgram(z,spans=1,detrend=F,plot=T)
}

ksppgram(128,4,1,1,1)
ksppgram(128,4,1,0,0)
ksppgram(128,4,.25,1,1)