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Sunaj

Adding probabilities together

4 posts in this topic

#1 ·  Posted (edited)

Just trying to wrap my head around some (very) basic math here by converting it into AU3 syntax, on this page (http://www.paulgraham.com/naivebayes.html) there is a good example of how to add two, or more, probabilities together. Here's the short version:

If a and b are the probabilities associated with two independent pieces of evidence [that someone is a basketball player], then combined they indicate a probability of:

       ab
-------------------
ab + ( 1 - a )( 1 - b )

So in this case our answer is:

         (.60)(.72)
-------------------------------
(.60)(.72) + (1 - .60)(1 - .72)

which is .794. There is a 79.4% chance that the person is a basketball player.

 

Now, any takes on how I would implement that simple math in autoit code? For now I've got:

$prbs = 0.60 + 0.72
$dividers = ((0.60+0.72))+((1-0.60)+(1-0.72))
$result = $prbs / $dividers
ConsoleWrite('$result: ' & $result & @CRLF)

And the output is "0.66" which certainly isn't right so I'm doing something wrong, any takers/helpers on this problem?

Edited by Sunaj

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ab = a * b, not a + b.

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If I posted any code, assume that code was written using the latest release version unless stated otherwise. Also, if it doesn't work on XP I can't help with that because I don't have access to XP, and I'm not going to.
Give a programmer the correct code and he can do his work for a day. Teach a programmer to debug and he can do his work for a lifetime - by Chirag Gude
How to ask questions the smart way!

I hereby grant any person the right to use any code I post, that I am the original author of, on the autoitscript.com forums, unless I've specifically stated otherwise in the code or the thread post. If you do use my code all I ask, as a courtesy, is to make note of where you got it from.

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ab = a * b, not a + b.

Ah so simple, thank you. After writing code to accumulate/calculate conditional probabilities (in PHP) I was stuck on how to combine them, this solves it nicely (and makes a good case for learning a bit of basic math notation), here's the fixed code in case someone should stumble on this subject down the road:

$prbs = 0.60 * 0.72
$dividers = ((0.60*0.72))+((1-0.60)*(1-0.72))
$result = $prbs / $dividers
ConsoleWrite('$result: ' & $result & @CRLF)

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It's been a LOOONNNGGG time since I've sat in a math class, good to know I haven't forgotten everything yet. ;)


If I posted any code, assume that code was written using the latest release version unless stated otherwise. Also, if it doesn't work on XP I can't help with that because I don't have access to XP, and I'm not going to.
Give a programmer the correct code and he can do his work for a day. Teach a programmer to debug and he can do his work for a lifetime - by Chirag Gude
How to ask questions the smart way!

I hereby grant any person the right to use any code I post, that I am the original author of, on the autoitscript.com forums, unless I've specifically stated otherwise in the code or the thread post. If you do use my code all I ask, as a courtesy, is to make note of where you got it from.

Back up and restore Windows user files _Array.au3 - Modified array functions that include support for 2D arrays.  -  ColorChooser - An add-on for SciTE that pops up a color dialog so you can select and paste a color code into a script.  -  Customizable Splashscreen GUI w/Progress Bar - Create a custom "splash screen" GUI with a progress bar and custom label.  -  _FileGetProperty - Retrieve the properties of a file  -  SciTE Toolbar - A toolbar demo for use with the SciTE editor  -  GUIRegisterMsg demo - Demo script to show how to use the Windows messages to interact with controls and your GUI.  -   Latin Square password generator

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