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# wexpcdf

## PURPOSE

Exponential cumulative distribution function

## SYNOPSIS

F = wexpcdf(x,m);

## DESCRIPTION

``` WEXPCDF Exponential cumulative distribution function

CALL:  F = wexpcdf(x,m);

F = distribution function evaluated at x
m = mean

The Exponential distribution is defined by its cdf

F(x)=1-exp(-x/m), x>=0, m>0.

Example:
x = linspace(0,6,200);
p1 = wexpcdf(x,1); p2 = wexpcdf(x,2);
plot(x,p1,x,p2)```

## CROSS-REFERENCE INFORMATION

This function calls:
 comnsize Check if all input arguments are either scalar or of common size. error Display message and abort function. nan Not-a-Number.
This function is called by:
 wexpfit Parameter estimates for Exponential data.

## SOURCE CODE

```001 function F = wexpcdf(x,m);
002 %WEXPCDF Exponential cumulative distribution function
003 %
004 % CALL:  F = wexpcdf(x,m);
005 %
006 %        F = distribution function evaluated at x
007 %        m = mean
008 %
009 % The Exponential distribution is defined by its cdf
010 %
011 %        F(x)=1-exp(-x/m), x>=0, m>0.
012 %
013 % Example:
014 %   x = linspace(0,6,200);
015 %   p1 = wexpcdf(x,1); p2 = wexpcdf(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
029
030 error(nargchk(2,2,nargin))
031 [errorcode x m] = comnsize(x,m);
032 if errorcode > 0
033     error('x and m must be of common size or scalar.');
034 end
035
036 % Initialize f to zero.
037 F = zeros(size(x));
038
039 k=find(x >= 0 & m>0);
040 if any(k),
041   F(k)=1-exp(-x(k)./m(k));
042 end
043
044 k3 = find(m<=0);
045 if any(k3)
046   tmp = NaN;
047   F(k3) = tmp(ones(size(k3)));
048 end
049```

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

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