[R] arrows

[Christian Hoffmann]

Suggestion:

Arrows is currently definded as:

arrows(x0, y0, x1, y1, length = 0.25, angle = 30, code = 2,
       col = par("fg"), lty = NULL, lwd = par("lwd"), xpd = FALSE)

length       length of the edges of the arrow head (in inches).

This definition is very rigid, the user has to convert inches on
screen/paper to user coordinates. I would suggest to add a paramter
"inches" like in "symbols":

symbols(x, y, circles, squares, rectangles, stars,
        thermometers, boxplots, inches=TRUE, add=FALSE,
        fg=1, bg=NA, xlab = "", ylab = "", xlim = NULL,
        ylim = NULL, ...)
inches    If inches is FALSE, the units are taken to be those of the x
axis. If inches is TRUE, the symbols are scaled so that the largest symbol
is one inch in height. If a number is given the symbols are scaled to make
largest symbol this height in inches.

As for the geometric length of the arrow heads in "arrows" with the new
parameter "inches": 
inches=FALSE: no problem (?)
inches=TRUE: no problem (?) 
inches=<number>: no problem (?).

Thanks for your consideration.
-christian
Dr.sc.math.Christian W. Hoffmann
Mathematics and Statistical Computing
Landscape Modeling and Web Applications
Swiss Federal Research Institute WSL 
Zuercherstrasse 111
CH-8903 Birmensdorf, Switzerland
phone: ++41-1-739 22 77    fax: ++41-1-739 22 15
e-mail: christian.hoffmann_at_wsl.ch__prevent_spamming
www: http://www.wsl.ch/staff/christian.hoffmann/

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