On Sep 21, 2010, at 10:50 AM, Daniel Stepputtis R wrote:
Dear group,
I have recognized a strange behaviour of palette(). I tried to find
any explanation but failed so far (or even didnt understood the idea
behind - what is most probable).
My original plan was to define a palette, save it in a variable and
use it later for an image-plot. One reason why I tried to store the
palette in a variable was, because I wanted to change individual
values (e.g. the first value to gray).
Interestingly, the palette is not defined correctly in the first
run, but in the second run.
No, you have misunderstood what was happening. Read the Value section
of hte help page. The returned value of a call to palette is the _old_
settings, (just like the par function). It allows a programming
strategy like:
oldvals <-func_with_side_effect(new_settings)
<Do stuff with new_settings in place>
func(oldvals)
Simple example:
>rm(list=ls())
> a <- palette(rainbow(6))
> a
[1] "red" "#FF4C00" "#FF9900" "#FFE500" "#CCFF00" "#80FF00"
"#33FF00" "#00FF19" "#00FF66" "#00FFB2" "cyan" "#00B3FF"
"#0066FF" "#0019FF" "#3300FF" "#8000FF" "#CC00FF"
[18] "#FF00E6" "#FF0099" "#FF004D"
> a <- palette(rainbow(6))
> a
[1] "red" "yellow" "green" "cyan" "blue" "magenta"
###################
Interestingly, this works at the first time
> palette(rainbow(20)) # six color rainbow
> plot(rnorm(20),col=1:20)
as well as
> palette(rainbow(6))
> a <- palette()
> a
[1] "red" "yellow" "green" "cyan" "blue" "magenta"
So, it seems to be that first a palette has to be defined (or set as
to be used) and then the vector can be assigned to a variable. I
dont understand why.
Thank you in advance for your help and explanation.
David Winsemius, MD
West Hartford, CT
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