Manually changing line size in ggplot

Question

Still getting to grips with ggplot. My question: How do I manually change the line size? I've tried with scale_size_manual but it didn't seem to work.

setup:

test.mat <- data.frame(matrix(nrow=32, ncol =3))
test.mat[,1] = rep(1:16,2)
test.mat[1:16,2] = as.character(rep("Cohort Alpha"),16)
test.mat[17:32,2] = as.character(rep("Factor Alpha"), 16)
test.mat[,3] = rnorm(32,0,1)
colnames(test.mat) = c("Window", "type", "value")

ggplot(test.mat, aes(x=Window, y=value)) +
  geom_line(aes(colour = type, linetype = type)) +
  theme_classic() +
  scale_colour_manual("type", values = c("black", "steelblue")) +
  scale_linetype_manual("type", values = c("solid", "solid")) +
  scale_size_manual("type", values = c(5, 1.4), guide = "none")

Maybe use size in geom_line? Most functions have a size argument anyways. Unless you have some other size mapping in mind, using the size arg should suffice. — NelsonGon
– NelsonGon, Commented Sep 28, 2019 at 11:47
@NelsonGon I have tried size = c(5,1.4)) but it doesn't work. Any suggestions — JC3019
– JC3019, Commented Sep 28, 2019 at 12:01
Your scale_size_manual is having no effect because you do not have a size aesthetic in your ggplot. Add size=type inside the aes(...) argument. — Andrew Gustar
– Andrew Gustar, Commented Sep 28, 2019 at 12:06
Try this: iris %>% ggplot(aes(Sepal.Length, size=Species, y=Petal.Length,color=Species))+ geom_point()+ geom_line()+ scale_size_manual(values=c(1,2,17)) — NelsonGon
– NelsonGon, Commented Sep 28, 2019 at 12:06

JC3019 · Accepted Answer · 2019-09-28 12:06:48Z

3

specify size inside aes() function as follows:

ggplot(test.mat, aes(x=Window, y=value)) +
  geom_line(aes(colour = type, linetype = type, size = type)) +
  theme_classic() +
  scale_colour_manual("type", values = c("black", "steelblue")) +
  scale_linetype_manual("type", values = c("solid", "solid")) +
  scale_size_manual("type", values = c(5, 1.4), guide = "none")

answered Sep 28, 2019 at 12:06

JC3019

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Community · Accepted Answer · 2020-06-20 09:12:55Z

0

Just turning @NelsonGon comment into an answer.

Is this what you want?

test.mat <- data.frame(matrix(nrow=32, ncol =3))
test.mat[,1] = rep(1:16,2)
test.mat[1:16,2] = as.character(rep("Cohort Alpha"),16)
test.mat[17:32,2] = as.character(rep("Factor Alpha"), 16)
test.mat[,3] = rnorm(32,0,1)
colnames(test.mat) = c("Window", "type", "value")
# -------------------------------------------------------------------------
base <- ggplot(test.mat, aes(x=Window, y=value)) 

#Here is where you need to add size  
line_size <- base + geom_line(aes(colour = type, linetype = type), size=3)
line_size + theme_classic() +
  scale_colour_manual("type", values = c("black", "steelblue")) +
  scale_linetype_manual("type", values = c("solid", "solid")) +
  scale_size_manual("type", values = c(5, 1.4), guide = "none")

output

Update

If you want variable thickness for the individual lines, you can do as follows.

base <- ggplot(test.mat, aes(x=Window, y=value)) 
#Use an ifelse to add variable thickness 
line_size <- base + geom_line(aes(colour = type, size=ifelse(type=="Cohort Alpha",1,2)))

line_size + guides(size = FALSE)

edited Jun 20, 2020 at 9:12

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answered Sep 28, 2019 at 11:57

deepseefan

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2 Comments

JC3019 Over a year ago

I want any arbitrary difference in the line sizes. These look the same size to me?

D. Bontempo Over a year ago

This is creating a mapping for size aesthetic that is numeric, so a range of increasing sizes from 1 to 2 (likely counting by .2) is used, and only the thinnest and thickest are used. A discrete mapping could be made with ifelse(type=="Cohort Alpha","thin","thick) - BUT thin will only be thinner if it is the 1st observed level. You could use factor(ifelse(type=="Cohort Alpha","thin","thick"), levels=c("thick","thin") - BUT to specify the actual sizes you also need + scale_size_manual(values = c(1.8, .75)). Or other thick and thin size choices.

D. Bontempo · Accepted Answer · 2021-02-23 20:29:51Z

0

To follow up on my comment on deepseefan's answer

base + 
  geom_line(aes(colour = type, 
                size=factor(ifelse(type=="Cohort Alpha", "thick",  "thin"),
                            levels=c("thick","thin")))) +
  scale_colour_manual(values = c("black", "steelblue")) +
  scale_size_manual(values = c(5, 1.4), guide = FALSE)

answered Feb 23, 2021 at 20:29

D. Bontempo

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