R help - Dec 2005 - Ploting graphics using X tints from a color

Hi,

I'm trying to draw a 2D plot using multiple tints of red. The
(simplified) setup is the following: || year | x | y ||

My idea is that each year is plotted with a different tint of red.
Older year (lightest) -> Later year (darkest). I've managed to plot
this with different scales of grays simply by doing:

palette(gray(length(years):0/length(years)))

before the plot and for each year the color used is a different tint of gray.

So, is there any way to do this for any color?
Any tip or advice?

With this, I hope to visualize patterns in my dataset more easily.

Thanks in advance for any help.

Best regards,
S??rgio Nunes

Le 13.12.2005 19:34, S??rgio Nunes a ??crit :
>Hi,
>
>I'm trying to draw a 2D plot using multiple tints of red. The
>(simplified) setup is the following: || year | x | y ||
>
>My idea is that each year is plotted with a different tint of red.
>Older year (lightest) -> Later year (darkest). I've managed to plot
>this with different scales of grays simply by doing:
>
>palette(gray(length(years):0/length(years)))
>
>before the plot and for each year the color used is a different tint of
gray.
>
>So, is there any way to do this for any color?
>Any tip or advice?
>
>With this, I hope to visualize patterns in my dataset more easily.
>
>Thanks in advance for any help.
>
>Best regards,
>S??rgio Nunes
>  
>
Hi,

You want to travel in the RGB space.
See http://addictedtor.free.fr/graphiques/RGraphGallery.php?graph=107

plot(0, xlim=c(0,10), ylim=c(0,1))
pal <- rgb(1, 0:10/10,0:10/10)
rect(xleft=0:9, xright=1:10, ytop=1, ybottom=0, col=pal)

Romain

-- 
visit the R Graph Gallery : http://addictedtor.free.fr/graphiques
mixmod 1.7 is released : http://www-math.univ-fcomte.fr/mixmod/index.php
+---------------------------------------------------------------+
| Romain FRANCOIS - http://francoisromain.free.fr               |
| Doctorant INRIA Futurs / EDF                                  |
+---------------------------------------------------------------+

> I'm trying to draw a 2D plot using multiple tints of red. The
> (simplified) setup is the following: || year | x | y ||
You might find this function useful:

map_colour_gradient <- function(x, low="red",
mid="white",high="black", midpoint = 0) {
	x <- as.numeric(x)
	low.rgb <- col2rgb(low, TRUE)/256
	mid.rgb <- col2rgb(mid, TRUE)/256
	high.rgb <- col2rgb(high, TRUE)/256

	interp_r <- approxfun(c(min(x, na.rm=TRUE), midpoint, max(x,
na.rm=TRUE)), c(low.rgb[1], mid.rgb[1], high.rgb[1]))
	interp_g <- approxfun(c(min(x, na.rm=TRUE), midpoint, max(x,
na.rm=TRUE)), c(low.rgb[2], mid.rgb[2], high.rgb[2]))
	interp_b <- approxfun(c(min(x, na.rm=TRUE), midpoint, max(x,
na.rm=TRUE)), c(low.rgb[3], mid.rgb[3], high.rgb[3]))

	
	rgb(interp_r(x), interp_g(x), interp_b(x))
}

Given a numeric vector x, it will create a smooth gradient (linearly
through RGB space).

eg.

x <- rnorm(100)
y <- rnorm(100)

plot(x, y, col=map_colour_gradient(x), pch=20)
plot(x, y, col=map_colour_gradient(x, low="black",
high="black",
mid="yellow"), pch=20)

Note, however, using colour is only likely to find the most prominent
of patterns.

Hadley

S伱仼rgio Nunes <snunes <at> gmail.com> writes:
> 
> Hi,
> 
> I'm trying to draw a 2D plot using multiple tints of red. The
> (simplified) setup is the following: || year | x | y ||
> 
> My idea is that each year is plotted with a different tint of red.
> Older year (lightest) -> Later year (darkest). 
 how about:

x = runif(300)
y = runif(300)
year = factor(rep(1:30,each=10))

nyear = length(levels(year))
grays = gray((nyear:0)/nyear)
reds = hsv(h=1,s=(0:nyear)/nyear,v=1)

plot(x,y,col=grays[as.numeric(year)],pch=16)
plot(x,y,col=reds[as.numeric(year)],pch=16)

plot(x,y,bg=reds[as.numeric(year)],pch=21,fg=1)
legend(0.8,1,levels(year),pch=21,pt.bg=reds,col=1,bg="white",ncol=2)

On Tue, 13 Dec 2005, S??rgio Nunes wrote:
> Hi,
> 
> I'm trying to draw a 2D plot using multiple tints of red. The
> (simplified) setup is the following: || year | x | y ||
> 
> My idea is that each year is plotted with a different tint of red.
> Older year (lightest) -> Later year (darkest). I've managed to plot
> this with different scales of grays simply by doing:
There have been other replies using rgb and hsv colour spaces directly,
but the new colorRamp and colorRampPalette functions iare worth mentioning
because they pack those solutions into a general framework:

years <- 1:20
plot(years, pch=19, col=grey(length(years):0/length(years)))

redPalette <- colorRampPalette(c("white", "red"))
plot(years, pch=19, col=redPalette(length(years)))

and the grey values can be reconstructed by:

greyPalette <- colorRampPalette(c("white", "black"))
plot(years, pch=19, col=greyPalette(length(years)))

with some values differing by 1 RGB unit. I've found colorRampPalette() 
very flexible, and that it supplements RColorBrewer well, so that 
intermediate colours can be interpolated for those palettes:

library(RColorBrewer)
redPalette <- colorRampPalette(brewer.pal(5, "Reds"))
plot(years, pch=19, col=redPalette(length(years)))

for a touch more tomato (subjectively) in the red.
> 
> palette(gray(length(years):0/length(years)))
> 
> before the plot and for each year the color used is a different tint of
gray.
> 
> So, is there any way to do this for any color?
> Any tip or advice?
> 
> With this, I hope to visualize patterns in my dataset more easily.
> 
> Thanks in advance for any help.
> 
> Best regards,
> S??rgio Nunes
> 
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