[R] Available in S-plus, also in R1.8.1?

[Uwe Ligges]

Hoeven, Maarten van der wrote:

> Agree, if a plot needs to be explained, something is not very well
> thought of. However, there are good rationals to do it this way.
> Moreover, I'm using R to replace SPSS-functionality (and imaging by
> pvwave) within a project, and I want to be close as possible to the
> image output of the preceeding project. Hence, this question.
> 
> The assumption is indeed an equidistant x-axis. This is true in my case.
> 
> What the stairstep-plot in R does (type="s" or type="S"), is to draw a
> horizontal line between two points on the x-axis. For example,
> 
> x1 = 1980
> x2 = 1981
> x3 = 1982
> y1 = 10
> y2 = 12
> y3 = 14
> 
> it draws a horizontal line between 1980 and 1981, at y-level 10 (or 12,
> depening on type="s" or type="S").
> 
> What I'm looking for, and this can be achieved in S+ by the mentioned
> connect type, is that the horizontal line *NOT* starts at exactly the
> x-values, but half between. See the attached example, where there is
> only one y-value of 1, at x=1995. You see the plot been drawn halfway
> 1995 (half before 1995, and half after 1995). This is what I'm look ing
> for. When using type="s" and type="S" in the plot-function, this would
> result in a polot that starts exactly at 1995, or ends exactly at 1995.
> I want to have it in between.

Now that I (hopefully) understand what you are going to do, the solution 
seems to be simple:

  x <- 1980:1982
  y <- c(10, 12, 14)

  n <- length(x)
  xdiff2 <- diff(x[1:2])/2
  x2 <- c(x - xdiff2, x[n] + xdiff2)
  y2 <- c(y, y[n])
  plot(x2, y2, type="s")


Uwe Ligges





> Thanks,
> 
> Maarten
> 
> 
> 
>>-----Original Message-----
>>From: Uwe Ligges [mailto:ligges at statistik.uni-dortmund.de]
>>Sent: Tuesday, February 10, 2004 10:11 AM
>>To: Hoeven, Maarten van der
>>Cc: r-help at stat.math.ethz.ch
>>Subject: Re: [R] Available in S-plus, also in R1.8.1?
>>
>>
>>Hoeven, Maarten van der wrote:
>>
>>
>>>Hi,
>>>
>>>I've send this one to the list last Thursday, no reaction yet. It's
>>>about the Connect Type in S+.
>>
>>In order to get an answer, you might want to be more specific what
>>"Connect type: half horiz first" really does in S-PLUS. I don't think 
>>something like that is available within an existing R 
>>function (I might 
>>be wrong here), but it can easily be coded (e.g. along the 
>>lines of code 
>>in package "stepfun"), given there is an *explicit 
>>definition* (and the 
>>cited URL is not very helpful here).
>>My question is: How do you define the "middle of a step", in 
>>particular 
>>if the interesting x values of your step-function are not equidistant?
>>
>>And another question: Why do you want to create a plot that 
>>needs to be 
>>explained? Other plots are much more intuitive (at least for me).
>>
>>Uwe Ligges
>>
>>
>>
>>
>>>===
>>>
>>>Hello all,
>>>
>>>I'm looking for the R-equivalent of the S-option "Connect type: half
>>>horiz first". Link:
>>>
>>
>>http://miner.stern.nyu.edu/Splus/help/guihelp/__hhelp/connect_type.htm
>>
>>>I'm plotting with type="s" or type="S"; this is giving me a 
>>
>>stairstep
>>
>>>starting, or ending with the value on the x-axis (as 
>>
>>documented). But, I
>>
>>>want the x-value in the middle of the step, like "half 
>>
>>horiz first" in
>>
>>>S-plus does.
>>>
>>>Is this possible in R?
>>>
>>>
>>>Thanks,
>>>Maarten
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>>>
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>>
>>http://www.R-project.org/posting-guide.html
>>
>>
> 
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