Dear Ted,

Thank you very much for your details explanation!

Cheers.

On Mon, Feb 13, 2012 at 7:12 PM, Ted Harding <Ted.Harding@wlandres.net>wrote:

> In addition to Jim's neat solution (see also below),
> some comments on your original code.
>
> Your "for" loop executes x=29.5 + i/500 100 times,
> producing a single value each time and replacing the
> previous value which was in x. So, at the end of the loop,
> you have a single value of x. Then you "compute" y=2x;
> that, as it stands, would prokoke an error:
>
>  Error: unexpected symbol in "y=2x"
>
> since variable names cannort start with a digit. You
> need, of course, the mutltiplaction operator "*" as
> in Jim's "y <- 2 * x".
>
> The scope of your "for" loop (i.e. the set of commands
> that is executed for each round of the loop) is solely
> the command "x=29.5 + i/500". The "y <- 2 * x" is not
> part of the scope of the loop, and would only be executed
> once, when the loop was finished. You would need
>
>   for(i in 1:1000) {
>     <commands>
>   }
>
> to cause the execution of several commands in each round
> of the loop.
>
> Finally, even if you did think that your entire series of
> commands (re-written):
>
>  for(i in 1:1000)
>  x=29.5 + i/500
>   y=2*x
>  plot(y,x)
>
> would all be executed (down to and including the plot() command)
> in each round of the loop, nevertheless each call to plot()
> creates a new graph, discarding the previous one, so only a single
> point would be plotted each time.
>
> The solution (as in Jim's suggestion) is to create the full vector
> of x-values and y-values, and then use plot(x,y) where x and y are
> now vectors.
>
> There are all sorts of little details about how R puts things
> together, which will become familiar as you use R. However,
> you do need to get hold of the basics of how R operates, so
> I would suggest having "R for Beginners"
>
>  http://cran.r-project.org/doc/contrib/Paradis-rdebuts_en.pdf
>
> to hand while you learn R. It is very good about how the basics
> work. The next step up would be the more systematic exposition
> of how R works in  "An Introduction to R":
>
>  http://cran.r-project.org/doc/manuals/R-intro.html
>  http://cran.r-project.org/doc/manuals/R-intro.pdf
>
> Hoping this helps!
> Ted.
>
> On 13-Feb-2012 jim holtman wrote:
> > x <- 29.5 + (1:1000)/500
> > y <- 2 * x
> > plot(y,x)
> >
> > On Mon, Feb 13, 2012 at 1:34 PM, eddie smith <eddieatr@gmail.com> wrote:
> >> Hi guys,
> >>
> >> This is a very beginner question. Anybody willing to help?
> >>
> >> for(i in 1:1000)
> >> x=29.5 + i/500
> >> y=2x
> >> plot(y,x)
> >>
> >> The idea is to produce 1000 values of x and y then plot them.
> >>
> >> Cheers,
> >> Eddie
> >>
> >> _ _ _ _[[alternative HTML version deleted]]
> >>
> >> ______________________________________________
> >> 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.
> >
> >
> >
> > --
> > Jim Holtman
> > Data Munger Guru
> >
> > What is the problem that you are trying to solve?
> > Tell me what you want to do, not how you want to do it.
> >
> > ______________________________________________
> > 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.
>
> -------------------------------------------------
> E-Mail: (Ted Harding) <Ted.Harding@wlandres.net>
> Date: 13-Feb-2012  Time: 19:12:47
> This message was sent by XFMail
> -------------------------------------------------
>

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