function biorhythm(birthday,plotday)
% BIORHYTHM Plot of your biorhythm for an 8 week period.
%
% BIORHYTHM('birthday','plotday')
% BIORHYTHM('birthday') uses today for plotday.
% BIORHYTHM with no arguments prompts for birthday.
% Example:
% biorhythm('July 6, 1946')
%
% Biorhythms were very popular in the '60's. You can still find
% many Web sites today that offer to prepare personalized biorhythms,
% or that sell software to compute them.
% Biorhythms are based on the notion that three sinusoidal cycles
% influence our lives. The physical cycle has a period of 23 days,
% the emotional cycle has a period of 28 days, and the intellectual
% cycle has a period of 33 days. For any individual, the cycles are
% initialized at birth.
%
% From "Numerical Computing with MATLAB"
% Cleve Moler
% The MathWorks, Inc.
% See http://www.mathworks.com/moler
% January 28, 2004. Copyright 2004.
if nargin < 1
birthday = input('When is your birthday? ','s')
end
if nargin < 2
plotday = datestr(fix(now));
end
t0 = datenum(birthday);
t1 = datenum(plotday);
clf
shg
axes('position',[.10 .30 .80 .50])
t = (t1-28):1:(t1+28);
y = 100*[sin(2*pi*(t-t0)/23); sin(2*pi*(t-t0)/28); sin(2*pi*(t-t0)/33)];
plot(t,y)
line([t1 t1],[-100 100],'color','k')
set(gca,'xtick',(t1-28):7:(t1+28))
datetick('x',6,'keeplimits','keepticks')
text(t1-3,-130,datestr(t1,1))
title(['birthday: ' datestr(birthday,1)])
axis tight
l1 = legend('Physical','Emotional','Intellectual');
set(l1,'pos',[.10 .02 .18 .12])
