From bug-octave-request at bevo dot che dot wisc dot edu  Mon Jan 24 12:20:18 2000
Subject: sign error in `weibull_pdf.m'
From: Cyril Humbert <humbert at phobos dot univ-mlv dot fr>
To: bug-octave at bevo dot che dot wisc dot edu
Date: Mon, 24 Jan 2000 12:20:36 -0600 (CST)

------- start of forwarded message -------

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
                



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