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qplot, stacked area, own colourscheme

3 messages · Albin Blaschka, Hadley Wickham

Albin Blaschka
# 
Dear list,

I would like to apply my own colours to a stacked area plot, done with 
qplot, but I have not succeeded...

What do I have so far (I am dealing with the development of cover of 
specific groups of plants):


library(ggplot2) 

library(RODBC) 

channel <- odbcConnect("myusername", case="tolower") 

sql <- "select trial, cover_of, dateofsurvey, cover from mytable" 

mydata <- (sqlQuery(channel, sql))

What I get is the following dataframe (simplified, there are more 
categories, not real data):

	trial	cover_of		dateofsurvey	cover
1        ZU-316 Cover dead material	2004-09-16    0
2        ZU-316 Cover grasses		2004-09-16   16
3        ZU-316 Cover herbs		2004-09-16   14
4        ZU-316 Cover legumes		2004-09-16   10
5        ZU-316 Cover open soil		2004-09-16   30
6        ZU-316 Cover dead material	2005-09-18    5
7        ZU-316 Cover grasses		2005-09-18   26
8        ZU-316 Cover herbs		2005-09-18   14
9        ZU-316 Cover legumes		2005-09-18   15
10       ZU-316 Cover open soil		2005-09-18   20
11       ZU-316 Cover dead material	2006-09-06    7
12       ZU-316 Cover grasses		2006-09-06   36
13       ZU-316 Cover herbs		2006-09-06   20
14       ZU-316 Cover legumes		2006-09-06   15
15       ZU-316 Cover open soil		2006-09-06   20
.
.
.

With the following command I get a nice graph (development of cover over 
the years):

qplot(dateofsurvey, cover, data=mydata, geom="area", fill=cover_of,
         main = "Development of cover, ZU-316",
         ylab="projective Cover[%]", xlab = "Year")

As I have those categories (cover grasses, cover herbs...) I would like 
to assign special colours to each (for example "cover grasses" => dark 
green, "cover open soil" => brown ...), but I did not get it so far.
I tried several variations with area_geom, scale_manual but without 
success...
For example (which does not work, it just shows the standard colourscheme):

mycolorscheme <- c("khaki", "darkgreen",
		   "lightgreen", "yellow", "saddlebrown")
mycolors <- rep(mycolorscheme,3)

myplot <- qplot(dateofsurvey, wert, data=mydata, geom="area",
		fill=cover_of, main = "Development of cover, ZU-316",
		ylab="projective Cover[%]", xlab = "Year")
myplot + geom_area(colour = mycolours)

What am I doing wrong?

Thank you in advance,
Albin
Hadley Wickham
# 
On Wed, Sep 24, 2008 at 8:39 AM, Albin Blaschka
<albin.blaschka at gmail.com> wrote:
You want to modify the scale (the thing that converts data values to
colours), not the geom:

+ scale_fill_manual(values = mycolorscheme)

(And it's fill you want to change, not colour)

This will also update the legend.

Hadley
Albin Blaschka
# 
hadley wickham schrieb:
[snip]
Thank you very much, it works now - the right keywords were the problem: 
it seems I went wrong because for me "scale" had only a meaning in a 
spatial context (mother tongue is german), for example scale on a map or 
scale (range) of an axis...and I was fixed to changeing colours, but 
fill is now logical...

best wishes,
Albin