From bug-octave-request at bevo dot che dot wisc dot edu  Mon Jan 24 16:46:20 2000
Subject: sign error in `weibull_pdf.m'
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: Cyril Humbert <humbert at phobos dot univ-mlv dot fr>
cc: bug-octave at bevo dot che dot wisc dot edu
Date: Mon, 24 Jan 2000 16:46:25 -0600 (CST)

On 24-Jan-2000, Cyril Humbert <humbert at phobos dot univ-mlv dot fr> wrote:

| weibull_pdf(x, alpha, beta) should compute
| 
|     alpha * sigma^(-alpha) * x^(alpha-1) * exp(-(x/sigma)^alpha)
| 
| but, in fact, it computes
| 
|     alpha * sigma^(+alpha) * x^(alpha-1) * exp(-(x/sigma)^alpha)
|                    |	       
|            
| --- 2.0.14/m/statistics/distributions/weibull_pdf.m~	Sun Sep  5 19:59:36 1999
| +++ 2.0.14/m/statistics/distributions/weibull_pdf.m	Mon Jan 24 18:31:44 2000
|  at @ -53,7 +53,7 @@
|    
|    k = find ((x > 0) & (x < Inf) & ok);
|    if any (k)
| -    pdf(k) = (shape(k) .* (scale(k) .^ shape(k))
| +    pdf(k) = (shape(k) .* (scale(k) .^ (-shape(k)))
|  	      .* (x(k) .^ (shape(k) - 1)) 
|  	      .* exp(- (x(k) ./ scale(k)) .^ shape(k)));
|    endif

I made this change in my sources.

Thanks,

jwe



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