Appendix - Rock Magnetic Cyclostratigraphy - page 150

r=randn(size(summer));
sdsummer=std(summer);
sdr=std(r);
noisysummer=summer+sdsummer*r/sdr;
figure;plot(time,noisysummer); % Figure 4.7b
fc=0.05;fl=fc-0.015;fh=fc+0.015;dt=1.;
gaussnoisysummer=gaussfilter(noisysummer,dt,fc,fl,fh);
figure;plot(time,gaussnoisysummer); % Figure 4.7c
tanernoisysummer=tanerfilter(noisysummer,dt,fc,fl,fh);
figure;plot(time,tanernoisysummer); % Figure 4.7d
% Import precession index file as 'data' (use File menu)
time=data(:,1);
precession=data(:,2);
figure;plot(time,precession); % Figure 4.7e
Note: Windows users can compute insolation and precession index series
with the online insolation calculator: http://www.imcce.fr/Equipes/ASD/
insola/earth/online/
Figure 4.8 Example of a real-valued time series of length 512 with two
closely spaced frequencies 0.050 and 0.055 and its FFT; plot the modulus of
the FFT:
t=1:1:512;
signal=sin(2*pi*t*0.05)+sin(2*pi*t*0.055);
figure;plot(signal);
y=fft(complex(signal));
mag=2*abs(y);
figure;plot(mag);
figure; plot(mag,'.-','markeredgecolor','k','marker
facecolor','k');
Figure 4.10 Effects of the Dirichlet (no taper), Bartlett, and Hann tapers on
the FFT are demonstrated.
tt=1:1:2048;
nn=length(tt);
signal=sin(2*pi*tt*0.05)+sin(2*pi*tt*0.055);
figure;plot(tt,signal);
barttaper=bartlett(nn);
bartsignal=barttaper.*signal'; % note transpose (')
of signal
figure;plot(tt,bartsignal);
hanntaper=hann(nn);
hannsignal=hanntaper.*signal';
figure;plot(tt,hannsignal);
% Dirichlet
xx=complex(signal);
y=fft(xx);
mag=2*abs(y);