How do you get MATLAB to print simplified expression in command window?

Hello,

I am working with a time domain function and can successfully plot it (figure 1) and plot its fourier transform (figure 3).

Now, I want to have MATLAB output the simplified expression, that the figure 3 fourier graph is based on, in the command window as a function. How can I do this?

Best regards.

% starting point
%------------------------
clear all;
close all;
N=4096; % N= number of points in the FFT
t=linspace(-1/2,1/2,N); % time span = 1 second
s = 10*rectpuls(5*t)
%------------------------


% Plot the input signal s(t)
figure(1);
clf;
plot(t,s,'linewidth',2); % plot the real input signal
hold on;
line( [-1/2 1/2],[0 0] ); % x-axis line
grid on;
ymax = max( abs(s) )*1.5; % ymax = plot scale factor
axis([-1/2 1/2 -ymax ymax]); % rescale
xlabel('Time (sec)');
ylabel('Amplitude');
title('s(t) defined on 1 sec centered at 0');


%------------------------
s = fftshift(s); % reorder the input signal
S = fft(s)/N; % S = Fourier transform
S = fftshift(S); % reorder the transform
n = -100:100; % define points near the origin
Sn = S(1+(N/2)+n); % Sn = points near the origin


figure(2);
plot(t,s,'linewidth',2); 
title('s(t) after rearranged by fftshift');
xlabel('Time (sec)');
ylabel('Amplitude');

energy_t = trapz(t, abs(s).^2 ) 
energy_f = trapz(t, abs(S).^2 )*N


%------------------------
% Plot real & imag Fourier transform S(f) near f=0
figure(3);
clf;
plot(n,real(Sn),'-b', 'markersize',2); % blue solid
hold on;
plot(n,imag(Sn),'--r','markersize',2); % red dashed
grid on;
axis([-100 100 -1.5 1.5]);
xlabel('Freq (Hz)');
ylabel('Amplitude');
title('Fourier Transform S(f)');

[Walter Roberson]

What simplified expression would that be? Are you trying to detect the peaks and create an expression along the lines of "the input was the sum of these three frequencies" ?