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wraylstat

PURPOSE ^

Mean and variance for the Rayleigh distribution.

SYNOPSIS ^

[m,v]= wraylstat(b);

DESCRIPTION ^

 WRAYLSTAT Mean and variance for the Rayleigh distribution.
  
  CALL:  [m,v] = wraylstat(b)
 
    m, v = the mean and variance, respectively 
       b = parameter of the Rayleigh distribution (see wraylcdf)
 
   Mean (m) and variance (v) for the Rayleigh distribution is
 
   m=b*(pi/2)^(1/2)  and  v=(2-pi/2)*b^2;
 
  Example:
    [m,v] = wraylstat(1/(pi/2)^(1/2))
 
  See also  wraylcdf

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

SOURCE CODE ^

001 function [m,v]= wraylstat(b);
002 %WRAYLSTAT Mean and variance for the Rayleigh distribution.
003 % 
004 % CALL:  [m,v] = wraylstat(b)
005 %
006 %   m, v = the mean and variance, respectively 
007 %      b = parameter of the Rayleigh distribution (see wraylcdf)
008 %
009 %  Mean (m) and variance (v) for the Rayleigh distribution is
010 %
011 %  m=b*(pi/2)^(1/2)  and  v=(2-pi/2)*b^2;
012 %
013 % Example:
014 %   [m,v] = wraylstat(1/(pi/2)^(1/2))
015 %
016 % See also  wraylcdf
017 
018 % Reference: Cohen & Whittle, (1988) "Parameter Estimation in Reliability
019 % and Life Span Models", p. 181 ff, Marcel Dekker.
020 
021 %tested on: matlab 5.3
022 % history
023 % revised pab 24.10.2000
024 % Added checks on b
025 
026 
027 
028 error(nargchk(1,1,nargin))
029 
030 %   Initialize Mean and Variance to zero.
031 m = zeros(size(b));
032 v = zeros(size(b));
033 
034 ok = (b > 0);
035 k = find(ok);
036 if any(k)
037  m(k) = b(k) * sqrt(pi/2);
038  v(k) = (2 - pi/2) * b(k) .^ 2;
039 end
040 
041 k1 = find(~ok);
042 if any(k1)
043     tmp = NaN;
044     m(k1) = tmp(ones(size(k1)));
045     v(k1) = m(k1);   
046 end
047 
048 
049 
050 
051 
052

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

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