Hi Folks,
I'm curious for an explanation of the following -- it's a
matter of trying to understand how R parses it.
I've written sundry little "helper" variants of functions,
in particular plot(), to save repetitively typing the same
options over and over again.
For example:
plotb <- function(x,...){plot(x,pch="+",col="blue",...)}
This does exactly what you'd expect it to do when fed with
a vector of values to plot, e.g.
plotb(cos(0.01*2*pi*(0:100)))
namely a plot of the values of cos(..) with x-coordinates
marked 0, 20, 40, 60, 80, 100, as blue "+".
As expected, one can add other plot options if needed, e.g.
plotb(cos(0.01*2*pi*(0:100)), xlim=c(0,4*pi))
if one wants. In this case, I'm supposing that the "xlim=c(0,4*pi)"
goes in under the umbrella of "...", which is what I guessed
would happen.
Interestingly, though, if I do
x<-0.01*2*pi*(0:100); plotb(x,cos(x))
I now get it with the x-axis labelled 0,1,2,3,4,5,6 just as
if I had used the built-in
x<-0.01*2*pi*(0:100); plot(x,cos(x),pch="+",col="blue")
and I can *also* add "xlim=c(0,4*pi)":
x<-0.01*2*pi*(0:100); plotb(x,cos(x),xlim=c(0,4*pi))
and it still works! Now the latter is the same "..." mechanism
as before, I suppose; but this doesn't explain how plotb()
"sees" x, along with cos(x), and picks it up to do the
right thing.
So my question -- which is why I'm posting -- is:
How does "x" get in along with "cos(x)" when I do
"plotb(x,cos(x))", when the definition of the function is
plotb <- function(x,...){plot(x,pch="+",col="blue",...)}
Thanks, and best wishes to all,
Ted.
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E-Mail: (Ted Harding) <[EMAIL PROTECTED]>
Fax-to-email: +44 (0)870 094 0861
Date: 07-Oct-07 Time: 20:49:26
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