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:[EMAIL PROTECTED] Sent: Tuesday, February 10, 2004 10:11 AM To: Hoeven, Maarten van der Cc: [EMAIL PROTECTED] 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 -------------------------------------------------------------- Zie ook/see also: http://www.knmi.nl/maildisclaimer.html
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