enerpwr.m

很多matlab的源代码

function p = enerpwr(x,d,T)
% ENERPWR Signal energy or signal power.
%
%         Y = ENERPWR(X,D) computes the ENERGY in X(t).
%
%	  If X is a string of t, D=[dlow, dhi], the duration limits:.
%         If X is a vector, D= [dlow, dhi, dt] includes the sampling interval.
%
%         Y = ENERPWR(X,D,TP) computes POWER in periodic X(t) with period TP. 
%
%         ENERPWR (with no arguments) invokes the following example:
%
%           % Find the power in a periodic signal whose one period is
%	    % 3*tri(t) over the duration (-1 1) and whose period is T=4
%           >>pwr=enerpwr('3*tri(t)',[-1 1],4);


% ADSP Toolbox: Version 2.0 
% For use with "Analog and Digital Signal Processing", 2nd Ed.
% Published by PWS Publishing Co.
%
% Ashok Ambardar, EE Dept. MTU, Houghton, MI 49931, USA
% http://www.ee.mtu/faculty/akambard.html
% e-mail: [e-mail]
% Copyright (c) 1998


if nargin==0,
 help enerpwr
 disp('Strike a key to see results of the example')
 pause
 pwr=enerpwr('3*tri(t)',[-1 1],4)
 return
end

if any(nargin==[2,3]),

 if length(d) < 2 & isstr(x),
  error('D must be of the form [dlow, dhi]');
 elseif length(d) < 3 & ~(isstr(x)),
  error('D must be of the form [dlow, dhi, dt]');
 end
 
 if nargin==3
  if T < abs(d(2)-d(1)),
   error('Pulse width cannot exceed period')
   return
  end
 end

 if isstr(x),
  y=['(' x ').*(' x ')'];
  p=simpson(y,d(1:2));
 else
  p=sum(x.*x)*d(3);
 end
 
 if nargin==3,
  p=p/T;
 end
 
elseif nargin == 1,
 error('Not enough input arguments');
elseif nargin > 3, 
 error('Too many input arguments');
end