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wexppdf

PURPOSE ^

Exponential probability density function

SYNOPSIS ^

f = wexppdf(x,m);

DESCRIPTION ^

 WEXPPDF Exponential probability density function 
  
  CALL:  f = wexppdf(x,m); 
  
         f = density function evaluated at x 
         m = mean 
  
  The Exponential distribution is defined by its pdf 
  
         f(x)=exp(-x/m)/m, x>=0, m>0. 
   
  Example:  
    x = linspace(0,6,200); 
    p1 = wexppdf(x,1); p2 = wexppdf(x,2); 
    plot(x,p1,x,p2)

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

SOURCE CODE ^

001 function f = wexppdf(x,m); 
002 %WEXPPDF Exponential probability density function 
003 % 
004 % CALL:  f = wexppdf(x,m); 
005 % 
006 %        f = density function evaluated at x 
007 %        m = mean 
008 % 
009 % The Exponential distribution is defined by its pdf 
010 % 
011 %        f(x)=exp(-x/m)/m, x>=0, m>0. 
012 %  
013 % Example:  
014 %   x = linspace(0,6,200); 
015 %   p1 = wexppdf(x,1); p2 = wexppdf(x,2); 
016 %   plot(x,p1,x,p2) 
017  
018 % Reference: Johnson, Kotz and Balakrishnan (1994) 
019 % "Continuous Univariate Distributions, vol. 1", p. 494 ff 
020 % Wiley 
021  
022 % Tested on; Matlab 5.3 
023 % History: 
024 %  Revised pab Dec2003 
025 % fixed abug k1->k3 
026 % revised pab 24.10.2000 
027 %  - added comnsize, nargchk 
028 % added ms 15.06.2000 
029  
030 error(nargchk(2,2,nargin)) 
031  
032 [errorcode x m] = comnsize(x,m); 
033 if errorcode > 0 
034     error('x and m must be of common size or scalar.'); 
035 end 
036  
037 % Initialize f to zero. 
038 f = zeros(size(x)); 
039  
040 k=find(x >= 0 & m>0); 
041 if any(k), 
042   f(k)=exp(-x(k)./m(k))./m(k); 
043 end 
044  
045 k3 = find(m<=0);      
046 if any(k3) 
047   tmp = NaN; 
048   f(k3) = tmp(ones(size(k3))); 
049 end 
050  
051  
052

Mathematical Statistics
Centre for Mathematical Sciences
Lund University with Lund Institute of Technology

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