Re: Need some help

You are right, I was a bit too vague. I am trying to simulate 1000 coin Tosses. Then to write a code for the number of heads/Tails.....naturally, we would expect the proportion of heads to be 50% so the number of heads would be around 500. Secondly, I'm trying to look at the number of sign changes in 1000 tosses. The example in the book shows that the number of sign changes is WAY less than 50%. so I was  trying to look for a code that shows the number of sign changes, which someone pointed out would be to use rle(x).....my concern however is that when the rle(x) is used, the proportion of sign changes is about 50% (around 500), which would be logical to expect, however, real life experiments have shown that the number of sign changes is actually much less than 50%. The other thing I was trying to do is to plot a line graph of number of sign changes versus the number of tosses. Yes, the number of tosses should begin at zero, and at zero coin toss, the sign change is zero. The range of the number of sign changes in the Y-axis should include negative values of Y. So, for toss number zero, the sign change is 0, for the first toss, the sign change may be +3 for instance, for the 50th toss, the sign change may be -5 for instance. The plot shown in the book shows that for most of the tosses, the sign changes were negative, and this would explain how the overall number of sign changes is very low.

so basically, i was looking for a code to show the number of sign changes,  and a plot of sign changes versus toss number (from toss #0 to toss number 1000). The Y axis (number of sign changes, should include negative values of Y)

thanks

Daniel Nordlund wrote:

> -----Original Message-----
> From: r-help-bounces@r-project.org [mailto:r-help-bounces@r-project.org] On Behalf
> Of azzza
> Sent: Monday, October 15, 2007 6:06 PM
> To: r-help@r-project.org
> Subject: Re: [R] Need some help
>
>
>
> Thanks Jholtman.
> However, the plot didnt come out the way I envisone dit to be. On the Y
> axis, i should have sign changes in 1000 tosses, the range being from
> negative to postitive, and a straight horizontal line across  y=0. The
> X-axis should have the toss number, range 0-1000
>

You would probably get more prompt and useful help if you would provide a small, self- contained example of what you wanted (maybe small enough that you could work it by hand).  Also, if you provided some code using the help that you have already received, that would show that you are trying to solve the problem yourself and others could help with the specific R program issues that you are having.  For example, it is not clear to me if you want to count the first run of tosses as 0 or 1 sign change.  I will assume it is zero.  So with that assumption, does this get you what you want?

n <- 1000
x <- sample(c(0,1), n, TRUE)
y <- rle(x)

z <- rep(1:length(y$lengths),y$lengths)
plot(1:n,z-1)

Hope this is helpful,

Dan

Daniel Nordlund
Bothell, WA USA

______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.