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Thread Subject:
Probability

Subject: Probability

From: Gema Olivarria

Date: 7 May, 2010 17:59:06

Message: 1 of 4

Hi this is my 3rd time using matlab i need help with something really simple. Here's my problem:

Start with point #1(i=1) whose coordinates are X(i)=0 and Y(i)=0.

Calculate the coordinates of the nxt point according to the following rule:

Randomly choose one of the following four events: A,B,C or D.
probability of A is 0.01;
probability of B is 0.06;
probability of C is 0.08;
probability of D is 0.85.

The coordinates of the nxt pt are:

If A occurred, X(i+1)=0, Y(i+1)=0.16Y(i);
If B occurred, X(i+1)=0.20X(i)-0.26Y(i), Y(i+1)=0.23X(i)+0.22Y(i)+1.6;
etc.,

My question is, how do i assign the probabilities to each of these functions? what syntax do i use?

Subject: Probability

From: us

Date: 7 May, 2010 18:12:04

Message: 2 of 4

"Gema Olivarria" <gforgamgee@yahoo.com> wrote in message <hs1kd9$evs$1@fred.mathworks.com>...
> Hi this is my 3rd time using matlab i need help with something really simple. Here's my problem:
>
> Start with point #1(i=1) whose coordinates are X(i)=0 and Y(i)=0.
>
> Calculate the coordinates of the nxt point according to the following rule:
>
> Randomly choose one of the following four events: A,B,C or D.
> probability of A is 0.01;
> probability of B is 0.06;
> probability of C is 0.08;
> probability of D is 0.85.
>
> The coordinates of the nxt pt are:
>
> If A occurred, X(i+1)=0, Y(i+1)=0.16Y(i);
> If B occurred, X(i+1)=0.20X(i)-0.26Y(i), Y(i+1)=0.23X(i)+0.22Y(i)+1.6;
> etc.,
>
> My question is, how do i assign the probabilities to each of these functions? what syntax do i use?

a this point in your ML life, you should dig into

http://www.mathworks.com/access/helpdesk/help/techdoc/learn_matlab/bqr_2pl.html

us

Subject: Probability

From: Roger Stafford

Date: 7 May, 2010 19:08:04

Message: 3 of 4

"Gema Olivarria" <gforgamgee@yahoo.com> wrote in message <hs1kd9$evs$1@fred.mathworks.com>...
> Hi this is my 3rd time using matlab i need help with something really simple. Here's my problem:
>
> Start with point #1(i=1) whose coordinates are X(i)=0 and Y(i)=0.
>
> Calculate the coordinates of the nxt point according to the following rule:
>
> Randomly choose one of the following four events: A,B,C or D.
> probability of A is 0.01;
> probability of B is 0.06;
> probability of C is 0.08;
> probability of D is 0.85.
>
> The coordinates of the nxt pt are:
>
> If A occurred, X(i+1)=0, Y(i+1)=0.16Y(i);
> If B occurred, X(i+1)=0.20X(i)-0.26Y(i), Y(i+1)=0.23X(i)+0.22Y(i)+1.6;
> etc.,
>
> My question is, how do i assign the probabilities to each of these functions? what syntax do i use?
- - - - - - - -
  Urs has given you excellent advice, Gema. However, I am guessing that if I give you the following matlab code as a hint for part of your problem without any explanation whatever, then having to figure out how and why it works and just what role it will play in your problem, should give you an added motivation to do the studying he recommends. I hope I am right.

 r = rand;
 k = (r<=.85)+(r<=.85+.08)+(r<=.85+.08+.06)+1;

Roger Stafford

Subject: Probability

From: Roger Stafford

Date: 7 May, 2010 19:25:06

Message: 4 of 4

  Please don't enter multiple threads with the same query, Gema. It creates resentment on the part of us who are endeavoring to answer you. I know I resent it.

Roger Stafford

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