Question about ggplot2: Changing fill colors with geom_area

[John Ramey]

Hello, everyone.

I am trying to update the graphics in my class notes with ggplot2.
Here I am displaying two continuous uniform distributions to show that
they have equal length and width. The two distributions are
Uniform(0,2) and Uniform(3,5).

The plots look good, but I do not know how to change the fill colors.
I have been unsuccessful with a number of scale_fill_* variants. Any
thoughts?

Here is my code:

a1 <- 0
b1 <- 2
a2 <- 3
b2 <- 5

x1 <- seq(a1, b1, by = 0.01)
x2 <- seq(a2, b2, by = 0.01)

y1 <- dunif(x1, a1, b1)
y2 <- dunif(x2, a2, b2)

df1 <- cbind.data.frame(x = x1, y = y1, Distribution = "Uniform(0,2)")
df2 <- cbind.data.frame(x = x2, y = y2, Distribution = "Uniform(3,5)")

df <- rbind(df1, df2)
df$Distribution <- factor(df$Distribution)

unif.loc.ggplot <- ggplot(df, aes(x = x, y = y, group = Distribution))
unif.loc.ggplot <- unif.loc.ggplot + geom_area(aes(fill =
Distribution))
unif.loc.ggplot <- unif.loc.ggplot + ylim(0.0, 1.0)
unif.loc.ggplot


Thanks in advance for any advice you can give.

[Dennis Murphy]

Hi:

Try this:

unif <- ggplot(df, aes(x = x, y = y, group = Distribution, fill = Distribution))
unif + geom_area() + ylim(0.0, 1.0) +
          scale_fill_manual(values = c('red', 'blue'))

HTH,
Dennis

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[Martin....@sanofi-aventis.com]

Hi,

I played around with the piece of code and got some weird behavior: (graphical output attached as pdf)

> library(ggplot2)

> df1<-cbind.data.frame(x=c(0,2),y=c(1/2,1/2),Distribution="Uniform(0,2)")

> df2<-cbind.data.frame(x=c(2,5),y=c(1/3,1/3),Distribution="Uniform(2,5)")

> df <-rbind(df1,df2)

> df$Distribution<-factor(df$Distribution)

> df

x y Distribution

1 0 0.5000000 Uniform(0,2)

2 2 0.5000000 Uniform(0,2)

3 2 0.3333333 Uniform(2,5)

4 5 0.3333333 Uniform(2,5)

> print(ggplot(df,aes(x=x,y=y,group=Distribution))

+ +geom_area(aes(fill=Distribution))+ylim(0,1))

> df$x[3]=df$x[3]+0.00000001

> df

x y Distribution

1 0 0.5000000 Uniform(0,2)

2 2 0.5000000 Uniform(0,2)

3 2 0.3333333 Uniform(2,5)

4 5 0.3333333 Uniform(2,5)

> print(ggplot(df,aes(x=x,y=y,group=Distribution))

+ +geom_area(aes(fill=Distribution))+ylim(0,1))

---

From: manip...@googlegroups.com [mailto:manip...@googlegroups.com] On Behalf Of Dennis Murphy
Sent: Thursday, September 23, 2010 4:41 AM
To: John Ramey
Cc: manipulatr
Subject: Re: Question about ggplot2: Changing fill colors with geom_area

[Dennis Murphy]

Hi:

> tail(df)
       x         y Distribution
198 1.97 0.5000000 Uniform(0,2)
199 1.98 0.5000000 Uniform(0,2)
200 1.99 0.5000000 Uniform(0,2)
201 2.00 0.5000000 Uniform(0,2)
202 2.00 0.3333333 Uniform(2,5)
203 5.00 0.3333333 Uniform(2,5)

You have two y's defined at x = 2.00. Add them up and the problem becomes clear.

HTH,
Dennis

[Martin....@sanofi-aventis.com]

(Sorry for the fragmented post.)

The right polygon appears to depend on the whether there are consecutive identical x values or not.
Could some expert please explain?

 Best regards

Dr. Martin Burschka

Sanofi-Aventis Deutschland GmbH
Industriepark Hoechst
Bldg. H831, Room B.0436
D-65926 Frankfurt am Main
w:www.sanofi-aventis.de

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---

From: Burschka, Martin R&D/DE
Sent: Thursday, September 23, 2010 1:35 PM
To: 'Dennis Murphy'; John Ramey
Cc: manipulatr
Subject: RE: Question about ggplot2: Changing fill colors with geom_area