[R] Aspect Ratio

[Peter Ehlers]

On 2010-08-19 16:36, r.ookie wrote:
> This example definitely clarified a situation where 'asp' is useful/helpful. Thanks!
>

Ted's last example is a bit misleading. You don't get the same
result from setting xlim and ylim equal as you do from using 'asp'.
Indeed, this should help you to understand aspect ratio even
better.

Try this:

  x11(width = 10, height = 5)
  plot(X,Y,pch="+",col="blue",xlim=c(-2.5,2.5),ylim=c(-2.5,2.5))

(using Ted's X,Y) and compare with the 'asp' version.

   -Peter Ehlers

> On Aug 19, 2010, at 3:05 PM, (Ted Harding) wrote:
>
> Spencer, you came up with your example just as I finished making mine:
>
>   set.seed(54321); X<- rnorm(200) ; Y<- 0.25*X+0.25*rnorm(200)
> ##Compare:
>   plot(X,Y,pch="+",col="blue")
> ##with:
>   plot(X,Y,pch="+",col="blue",asp=1.0)
>
> With R left to choose the X and Y limits by itself, the first
> plot gives the superficial impression that Y increases equally
> as X increases -- until you look at the scales on the Y and X
> axes. Hence it tends to be misleading about how Y depends on X.
> The second plot shows their proportional relationship correctly.
>
> Of course you could achive a similar effect by explicitly setting
> the X and Y limits yourself:
>
> plot(X,Y,pch="+",col="blue",xlim=c(-2.5,2.5),ylim=c(-2.5,2.5))
>
> but "asp=1.0" saves you the bother of working out what they
> should be.
>
> There are, of course, cases where, for the sake of the desired
> visual effect, you would want to use an aspect ratio different
> from 1. The basic point is that it is a tool to help you get
> the vertical and horizontal dimensions of the graph in the
> proportions that help to achieve the visual effect you seek.
>
> Ted.
>
> On 19-Aug-10 21:50:12, Spencer Graves wrote:
>>         The documentation is not clear.  It would help if it had an
>> example like the following:
>>
>> plot(1:2, 1:2/10)
>> plot(1:2, 1:2/10, asp=1)
>>
>>        Does looking at these two plots answer the question?
>>        Spencer Graves
>>
>> On 8/19/2010 2:36 PM, David Winsemius wrote:
>>>
>>> On Aug 19, 2010, at 5:28 PM, r.ookie wrote:
>>>
>>>> Well, I had to look further into the documentation to see 'If asp is
>>>> a finite positive value then the window is set up so that one data
>>>> unit in the x direction is equal in length to asp * one data unit in
>>>> the y direction'
>>>>
>>>> Okay, so in what situations is the 'asp' helpful?
>>>
>>> It yet again appears that you are asking us to read the help pages for
>>> you.
>>>
>>>
>>>>
>>>> On Aug 19, 2010, at 2:24 PM, David Winsemius wrote:
>>>>
>>>>
>>>> On Aug 19, 2010, at 5:13 PM, r.ookie wrote:
>>>>
>>>>> set.seed(1)
>>>>> x<- rnorm(n = 1000, mean = 0, sd = 1)
>>>>> plot(x = x, asp = 2000)
>>>>>
>>>>> Could someone please explain what the 'asp' parameter is doing?
>>>>
>>>> You want us to read the help page to you?
>>>>
>>>> --
>>>
>>> David Winsemius, MD
>>> West Hartford, CT
>>>
>>> ______________________________________________
>>> R-help at 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.
>>>
>>
>> --
>> Spencer Graves, PE, PhD
>> President and Chief Operating Officer
>> Structure Inspection and Monitoring, Inc.
>> 751 Emerson Ct.
>> San José, CA 95126
>> ph:  408-655-4567
>>
>> ______________________________________________
>> R-help at 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 at manchester.ac.uk>
> Fax-to-email: +44 (0)870 094 0861
> Date: 19-Aug-10                                       Time: 23:05:49
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