Plot values with facet_wrap using ggplot2

Question

I have a matrix:

mat<-matrix(NA, ncol=7,nrow=9) 
mat[,1]<-c(0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9) 
mat[,2]<-c(2,4,5,6,7,7,7,8,9) 
mat[,3]<-c(2,48,63,72,81,100,100,100,100) 
mat[,4]<-c(1,2,3,3,4,4,5,5,6) 
mat[,5]<-c(1,2,6,7,8,8,9,10,10) 
mat[,6]<-c(1,1,1,2,3,3,4,4,4) 
mat[,7]<-c(1,1,1,3,4,4,4,5,5)

colnames(mat)<-c("facet","A1","A2","B1","B2","C1","C2")

      facet A1  A2 B1 B2 C1 C2
 [1,]   0.1  2   2  1  1  1  1
 [2,]   0.2  4  48  2  2  1  1
 [3,]   0.3  5  63  3  6  1  1
 [4,]   0.4  6  72  3  7  2  3
 [5,]   0.5  7  81  4  8  3  4
 [6,]   0.6  7 100  4  8  3  4
 [7,]   0.7  7 100  5  9  4  4
 [8,]   0.8  8 100  5 10  4  5
 [9,]   0.9  9 100  6 10  4  5

I would like to create the following plot:

Create 9 separate plots faceted by "facet". Each plot should contain the following:

on the same position on the x axis plot A1 and A2 using points, i.e. (X=1, y=A1) and (X=1,y=A2)
on the same position on the x axis plot B1 and B2 using points, i.e. (X=2, y=B1) and (X=2,y=B2)
on the same position on the x axis plot C1 and C2 using points, i.e. (X=3, y=C1) and (X=3,y=C2)

How can this be done? I understand how to do faceting but I'm struggling with plotting the two values in the same position on the x axis and repeating for each A,B and C. can someone help?

Sven Hohenstein · Accepted Answer · 2013-12-03 13:41:25Z

1

First, reshape your matrix to a data frame in the long format:

library(reshape2)
dat <- melt(as.data.frame(mat), id.vars = "facet")

> head(dat)
#   facet variable value
# 1   0.1       A1     2
# 2   0.2       A1     4
# 3   0.3       A1     5
# 4   0.4       A1     6
# 5   0.5       A1     7
# 6   0.6       A1     7

Then, create two variables based on the information in the column variable:

dat2 <- transform(dat, fac = substr(variable, 2, 2),
                       variable = substr(variable, 1, 1))

> head(dat2)
#   facet variable value fac
# 1   0.1        A     2   1
# 2   0.2        A     4   1
# 3   0.3        A     5   1
# 4   0.4        A     6   1
# 5   0.5        A     7   1
# 6   0.6        A     7   1

Plot:

library(ggplot2)
ggplot(dat2, aes(x = variable, y = value)) +
  geom_point(aes(colour = fac)) +
  facet_wrap( ~ facet)

enter image description here

answered Dec 3, 2013 at 13:41

Sven Hohenstein

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4 Comments

user1723765 Over a year ago

can you explain how to do this when insead of A B C I have more variables? what needs to be modified in dat2?

Sven Hohenstein Over a year ago

@user1723765 This code is independent of the number of columns. Did you try it?

user1723765 Over a year ago

just a final thing: how do I change the colours of fac? I tried scale_fill_manual() but it didn't do anything

Sven Hohenstein Over a year ago

@user1723765 For your example you can try to add the following to your plot: scale_colour_manual(values = c("blue", "red")).

D L Dahly · Accepted Answer · 2013-12-03 14:17:02Z

0

 a <- cbind(mat[, 1], mat[, 2], 1, 1)
 b <- cbind(mat[, 1], mat[, 3], 1, 2)
 c <- cbind(mat[, 1], mat[, 4], 2, 1)
 d <- cbind(mat[, 1], mat[, 5], 2, 2)
 e <- cbind(mat[, 1], mat[, 6], 3, 1)
 f <- cbind(mat[, 1], mat[, 7], 3, 2)

 data <- as.data.frame(rbind(a, b, c, d, e, f))

 colnames(data) <- c("facet", "value", "type", "time")

 data$type <- factor(data$type, labels = c("A", "B", "C"))

 ggplot(data, aes(y = value, x = type, fill = factor(time))) +
        geom_point(aes(color = factor(time)), 
                   position = position_jitter(w = 0.1, h = 0.0))+
        facet_wrap(~facet)

enter image description here

edited Dec 3, 2013 at 14:17

answered Dec 3, 2013 at 14:00

D L Dahly

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