postscript(file="correlation.fig")
par(mfrow=c(4,0))
x4<-fft(rep(c(rep(1,10),rep(0,230)),100))/(24000)
x4.x<-rep(c(rep(1,10),rep(0,230)),100)
plot(x4.x[1:121],type="l")
plot(Re(fft((Conj(x4)*x4),-1))[1:121],type="l")
plot(x4.x[1:1201],type="l")
plot(Re(fft((Conj(x4)*x4),-1))[1:1201],type="l")
graphics.off()