Available in S-plus, also in R1.8.1?

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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Available in S-plus, also in R1.8.1?

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