# [R] Need some help

jim holtman jholtman at gmail.com
Mon Oct 15 19:07:44 CEST 2007

```I really depends on what you want to plot.  You can plot the
cumulative count of the sign changes with:

x <- sample(c(0,1), 1000, TRUE)
plot(cumsum(x), type='l')

There are other things you can do.  You can get a rough histogram of
the length of the run by:

> stem(rle(x)\$length)

The decimal point is at the |

1 | 00000000000000000000000000000000000000000000000000000000000000000000+201
1 |
2 | 00000000000000000000000000000000000000000000000000000000000000000000+60
2 |
3 | 00000000000000000000000000000000000000000000000000000
3 |
4 | 00000000000000000000000000000000000000
4 |
5 | 000000000
5 |
6 | 00000000
6 |
7 | 00000

With R, almost anything is possible.

On 10/15/07, azzza <azza.khogaliali at utoronto.ca> wrote:
>
> Umm, yes, what you had makes a lot of sense. How would I represent that in a
> plot of the number of sign changes in the to  Y axis, and the toss number
> (from 0 to 1000) in the x-axis?
>
>
>
>
> jholtman wrote:
> >
> > You might want to check out 'rle'.  This will give you the 'lengths'
> > of runs of the same value and therefore when the value changes (sign
> > change?) you can see how often:
> >
> >> x <- sample(c(-1,1), 1000, TRUE)
> >> rle(x)
> > Run Length Encoding
> >   lengths: int [1:483] 2 2 1 4 3 1 1 1 1 2 ...
> >   values : num [1:483] -1 1 -1 1 -1 1 -1 1 -1 1 ...
> >
> > Here was a sample of 1000, and there were 483 changes between the
> > samples.  Is this what you are looking for?
> >
> > On 10/15/07, azzza <azza.khogaliali at utoronto.ca> wrote:
> >>
> >>
> >> Quite helpful indeed. Greatly appreciated.
> >> Another problem I had was trying to simulate an example from my book.
> >> Simulating 1000 coin tosses, and finding the frequency of sign changes.
> >> So
> >> how will we plot this using R? (frequency of sign changes in Y axis)
> >>
> >>
> >>
> >>
> >> Daniel Nordlund wrote:
> >> >
> >> >> -----Original Message-----
> >> >> From: r-help-bounces at r-project.org
> >> [mailto:r-help-bounces at r-project.org]
> >> >> On Behalf
> >> >> Of azzza
> >> >> Sent: Sunday, October 14, 2007 10:21 PM
> >> >> To: r-help at r-project.org
> >> >> Subject: [R] Need some help
> >> >>
> >> >>
> >> >> Hi!
> >> >> I'm taking a course that requires some programming background, but I'm
> >> a
> >> >> complete novice in the field.
> >> >>
> >> >> when asked to generate a list of 20 uniform random numbers, is it
> >> alright
> >> >> if
> >> >> I put in >randu, and just copy-paste the first 20 numbers?? Or is
> >> there,
> >> >> as
> >> >> I suspect, a better way of calling out exactly 20 uniform random
> >> >> numbers??
> >> >>
> >> > See ?runif
> >> >
> >> > rand_nums <- runif(20)
> >> >
> >> >> I'm also unable to solve the following problem:
> >> >> We know that on average 30% of the customers who enter a store make a
> >> >> purchase. Suppose 200
> >> >> people enter the store today. Run a simulation to see how many
> >> purchases
> >> >> we
> >> >> will have today.
> >> >>
> >> > see ?sample
> >> >> number_of_purchases <- sum(sample(c(0,1), 200, prob=c(.70, .30),
> >> >> replace=TRUE))
> >> >
> >> > Hope this is helpful,
> >> >
> >> > Dan
> >> >
> >> > Daniel Nordlund
> >> > Bothell, WA USA
> >> >
> >> > ______________________________________________
> >> > R-help at r-project.org mailing list
> >> > https://stat.ethz.ch/mailman/listinfo/r-help
> >> > http://www.R-project.org/posting-guide.html
> >> > and provide commented, minimal, self-contained, reproducible code.
> >> >
> >> >
> >>
> >> --
> >> View this message in context:
> >> http://www.nabble.com/Need-some-help-tf4624513.html#a13214128
> >> Sent from the R help mailing list archive at Nabble.com.
> >>
> >> ______________________________________________
> >> R-help at r-project.org mailing list
> >> https://stat.ethz.ch/mailman/listinfo/r-help
> >> http://www.R-project.org/posting-guide.html
> >> and provide commented, minimal, self-contained, reproducible code.
> >>
> >
> >
> > --
> > Jim Holtman
> > Cincinnati, OH
> > +1 513 646 9390
> >
> > What is the problem you are trying to solve?
> >
> > ______________________________________________
> > R-help at r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
> >
>
> --
> View this message in context: http://www.nabble.com/Need-some-help-tf4624513.html#a13216156
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> and provide commented, minimal, self-contained, reproducible code.
>

--
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?

```