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Re: Location of probability PDF's and CDF's in gnuplot?


From: Paul Kienzle
Subject: Re: Location of probability PDF's and CDF's in gnuplot?
Date: Sat, 27 Aug 2005 00:44:51 -0400


Avocado:~ paulkienzle$ locate prob.dem
/sw/share/doc/gnuplot/demo/prob.dem
/Users/paulkienzle/darwinports/dports/math/gnuplot/work/gnuplot-3.8h.0/ demo/prob.dem


The functions are defined in stat.inc in the same directory. For logistic it is:

        # Logistic PDF
        logistic(x)=lambda*exp(-lambda*(x-a))/(1.0+exp(-lambda*(x-a)))**2

Note that many statistical functions are defined in Octave, though in the case of logistic_pdf, it does not include the lambda and a parameters so you instead need to use:

        y = lambda*logistic_pdf(lambda*(x-a))

to get the same function as gnuplot.

- Paul


On Aug 26, 2005, at 11:15 PM, Henry F. Mollet wrote:

Where are the probability PDF's and CDF's located in gnuplot so I can set the path that they can be found. When in my home directory and trying for example 'logistic(x)' the function cannot be found. After I load the demo 'prob.dem' and do a few functions and then quit, plot logistic(x) will work
using my own parameters for a and lambda.
Henry

gnuplot> show loadpath
        loadpath is "/usr/local/share/gnuplot/demo/"
"/usr/local/bin/gnuplot"
        system loadpath is
gnuplot> pwd
/Users/hfm
gnuplot> plot logistic(x)
         undefined function: logistic

gnuplot> load 'prob.dem'
                   Statistical Library Demo, version 2.3
          Copyright (c) 1991, 1992, Jos van de Woude, address@hidden
NOTE: contains 54 plots and consequently takes a lot of time to run
                      Press Ctrl-C to exit right now
                      Press Return to start demo ...
Hit return to continue^C
gnuplot> plot logistic(x)  # Now I get a graph
gnuplot>

I assume that default value would be used for the parameters if I don't give
them but this is not the problem:
gnuplot> plot logistic (x)
         undefined function: logistic
gnuplot> a = 0.0
gnuplot> lambda = 2.0
gnuplot> mu = a
gnuplot> sigma = pi/(sqrt(3.0) + lambda)
gnuplot> plot logistic (x)
         undefined function: logistic






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Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.octave.org
How to fund new projects:  http://www.octave.org/funding.html
Subscription information:  http://www.octave.org/archive.html
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