From bug-request at octave dot org Thu Nov 24 10:29:59 2005
Subject: Re: weibull functions
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: Ben Barrowes <barrowes at alum dot mit dot edu>
Cc: Quentin Spencer <qspencer at ieee dot org>, bug@octave.org
Date: Thu, 24 Nov 2005 11:27:20 -0500

On 23-Nov-2005, Ben Barrowes wrote:

| ML did use those names but has changed with the advent of stat TB 4.1:
| http://www.mathworks.com/access/helpdesk/help/toolbox/stats/rn/f2-54017.html
| 
| In addition, they changed their definitions in the weib*** functions, e.g.:
| >> life = wblinv(0.5, 200, 6)          
| life =
|           188.148563055955
| >> life = weibinv(0.5, 200, 6)
| life =
|          0.389014608848543
| >> 
| 
| and
| 
| >> life = wblpdf(0.5, 200, 6) 
| life =
|              2.9296875e-15
| >> life = weibpdf(0.5, 200, 6)
| life =
|           1.64763501087778
| >> 
| 
| 
| These changes, brought ML more in line with the rest of the stats community.
| 
| 
| I am not sure how long the weib*** were being used in ML, but I
| think for a few years. We may want to keep the wrapper for
| compatibility.

Then it seems that the functions like this

  function pdf = weibpdf (varargin)
    pdf =  wblpdf (varargin{:});
  endfunction

that you posted in another message would not be correct, as it makes
the behavior of weibpdf and wblpdf exactly the same.

If you want these changes adopted in Octave, then please send a single
corrected patch that does the following:

  * introduces wbl* functions that are compatible with the current
    version of the corresponding Matlab functions

  * moves weib* functions to deprecated, preserving the current
    functionality (assuming that the current behavior is correct and
    compatible with the corresponding Matlab functions; if it is not,
    then the functions should be corrected to be compatible).

If the only significant difference between the wbl* and weib*
functions is the order of the arguments, then the real implementation
should be in the wbl* functions and the weib* and weibull* functions
should be implemented in terms of those functions by rearranging the
argument lists as necessary.

Please send this as a patch that I can apply rather than as a
collection of new functions pasted into a mail message.

Thanks,

jwe



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