Bayes' Theorem

model · 2012-01-31 19:47:41

Hy guys ,

I did not understand the basic meaning and purpose of Bayes' Theorem . Could any one please elaborate a bit .
Thanks

Bob · 2012-01-31 21:34:58

Hi model

I am not able to draw you a diagram at the moment
but you can look up the one I did recently in thread 17078.

Say you take a card from a pack and then another.

The probability of card two being an ace (let's say )
Will depend on whether card one was an ace.

P(second ace given first ace) = 3/51

But

P(second ace given first not) = 4/51

I have always found a diagram like 17078 sorts out
Most two event problems.

Bob

model · 2012-02-01 19:39:58

Hy ,

17078 is my question thread . and where is diagram as you said in your posted reply ?

MathsIsFun · 2012-02-01 22:56:17

Try http://www.mathisfunforum.com/viewtopic.php?id=17078

model · 2012-02-01 23:00:52

MathsIsFun wrote:

Try http://www.mathisfunforum.com/viewtopic.php?id=17078

thanks for the link .

model · 2012-02-10 19:36:06

Hy I understood Bayes theorem and Bayesian network .

Let say my hand started motion at point A that initial position what would be the next position of my hand at point B?

like as shown in this image : http://imageshack.us/photo/my-images/213/10901168.png/

My question is how to know the probability of point A ?

kanta · 2012-02-10 20:23:04

Sophia sets off on a walk at a speed of 6 km/h.ten minutes later,her brother Danish sets off after her on his bicycle at 15 km/h. How far must Danish go to catch up with sophia?

please solve.

bobbym · 2012-02-10 22:22:55

Hi kanta;

Please post a new thread when you post a new problem. Just tacking it on to someone else's hides their post.

So Danish catches Sophia after 1 / 9 hrs. To get how far he travels

So Danish travels 5 / 3 km.

model · 2012-02-10 22:52:14

HY Bobbym ,

What about my question ?

Last edited by model (2012-02-10 22:52:58)

bobbym · 2012-02-10 22:53:05

Hi model;

I am looking at it now.

bobbym · 2012-02-10 23:02:57

Hi model;

I think we need more information to determine the probability of point A. Do you have any more?

model · 2012-02-10 23:15:55

bobbym wrote:

Hi model;
I think we need more information to determine the pobability of point A. Do you have any more?

Hy no, I do't have any information.

but yes one thing. we could consider that 10 frames passed then object moved . I am also thinking what type of information do i need to get probability of point A.

bobbym · 2012-02-10 23:18:31

You would need to know what part of the graph you can place A and the number of horizontal and vertical pixels of that area.

model · 2012-02-10 23:23:36

bobbym wrote:

You would need to know what part of the graph you can place A and the number of horizontal and vertical pixels of that area.

Do you mean that how much point A covered his distance and area ?

bobbym · 2012-02-10 23:25:42

Isn't point A the initial point? The first one?

model · 2012-02-10 23:28:33

bobbym wrote:

Isn't point A the initial point? The first one?

hmm yes .. right . ok point A is initial point. meant current location.
then what do you mean by this

" You would need to know what part of the graph you can place A and the number of horizontal and vertical pixels of that area. "

Do you meant by moving object area ? like my hand area ?

Last edited by model (2012-02-10 23:30:30)

bobbym · 2012-02-10 23:31:17

If you were to draw an imaginary rectangle around the area where Point A could be placed where would it be?

model · 2012-02-10 23:35:45

bobbym wrote:

If you were to draw an imaginary rectangle around the area where Point A could be placed where would it be?

hmm hold on. lemme post here total image size in form of rectangle area . and a point A(i-e hand) with its coordinates x and y . ok

Last edited by model (2012-02-10 23:37:21)

model · 2012-02-10 23:53:09

Hy,

my image area is : 76800

and hand area is : 4592

you can see in this image as link : http://imageshack.us/photo/my-images/823/imgoy.png/

And now tell me what info do we need to get the probability of my hand as a point A ?

Last edited by model (2012-02-10 23:54:39)

bobbym · 2012-02-10 23:57:28

Hold on for a second. Let's go back to post #6. We are looking at a graph which might represent your screen. Can point A start anywhere on the screen? We need to know what is the possible spots where A can be placed initially?

model · 2012-02-11 00:19:02

well initial location of my hand is 0 when there is no hand appear in the video but when hand appear any where in the video then location will appear . Hy please consider #6 for my work as i shown in the image.

bobbym · 2012-02-11 06:02:44

Hi model;

Unless we can get the problem down to something like post #6 we will not be able to say anything about the probabilty.

I will draw you a diagram that will hopefully explain what we need.

model · 2012-02-11 21:08:38

bobbym wrote:

Hi model;
Unless we can get the problem down to something like post #6 we will not be able to say anything about the probabilty.
I will draw you a diagram that will hopefully explain what we need.

hmm ok i am waiting for your diagram then .
and yes thanks for helping me.

bobbym · 2012-02-11 22:15:05

Hi model;

model · 2012-02-12 17:47:17

bobbym wrote:

Hi model;

I think you meant by this is area of point A, right ?

Math Is Fun Forum

#1 2012-01-31 19:47:41

Bayes' Theorem

#2 2012-01-31 21:34:58

Re: Bayes' Theorem

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