[R] random value changes in a vector

[David Winsemius]

It's generally better to have a descriptive subject as you have done  
here but not in your prior psoting.

You might think about how you can use this sort of result:

vec <- c(1, -1, -1, 1, 1, -1)
sample(c(-1,1),length(vec),replace=T)

Perhaps:
vec <- vec*sample(c(-1,1),length(vec),replace=T)

?sample  # should explain how probabilities other than 0.5 can be  
specified

On Nov 18, 2008, at 12:11 PM, Salas, Andria Kay wrote:

> To clear up a question regarding my earlier posting regarding random  
> changes in a vector:
>
> Say you have a vector (1, -1, -1, 1, 1, -1).  I want each value in  
> the vector to have a probability that it will change signs when this  
> vector is regenerated.  For example, probability = 50%.  When the  
> vector is regenerated, the first value in the vector (1) has a 50%  
> chance of switching to -1.  If I regenerated this vector 10 times, 5  
> of the times it would switch to -1.

Only "on average" would that be true. It might not switch at all if  
the process is truly random.

-- 
David Winsemius

> Similarly, I need each value in the vector to have this same  
> probability of switching signs when the vector is regenerated, and  
> each value's chances of doing so is independent of the other  
> values.  So the second value (-1) also has a 50% chance of switching  
> to 1, and whether or not it does so is independent of if the first  
> value changes from 1 to -1 (also a 50% probability).
>
> I hope this clears up the confusion, and I would appreciate any help  
> anyone can provide!
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