function [t3, w3, z3]=psd3d(w, p, w1, t0, t1);

% The function PSD3D computes the variables, t3, w3, z3 for 3-D Fourier Spectrum plots. 
% Computed Fourier spectrum variables w and p are passed to the function.
%			 
% For a desired frequency range wd: 
% w1=wd*window size/ sampling rate (pick the nearest integer).
% Number of points in time axis is fixed at 10.
% The final result represents the surface: surf(t3, w3, z3).
%
% Calling sequence-
% [t3, w3, z3]=psd3d(w, p, w1, t0, t1)
%
% Input-
%	w	- frequency from psd
%		Length of w = 1/2 window size
%		Range of  w = 1/2 sampling rate
%	p	- power spectral density from psd
%	w1	- total number of points,
%		(<w), in frequency used in the 3-D plot
%	t0	- true initial time
%	t1	- true end time
% Output-
%	t3	- X- axis values
%	w3	- Y- axis values
%	z3	- Z- axis values
 
% Norden Huang (NASA GSFC)   November 12 1999

pp=p(1:w1);
ww=w(1:w1);
z3=zeros(w1, 10);

for i=1:w1;
	z3(i, :)=pp(i)*ones(1, 10);   
end

t3=linspace(t0, t1, 10);
t3=t3';
w3=w(1:w1); 

surf(t3, w3, z3);
shading interp;
view(120, 40);
xlabel('Time : ..');
ylabel('Frequency : ..');
zlabel('Spectral Density');