r - Plot multiple columns with labels in one graph

Question

I would like to plot 3 columns data (x,y,z) by time in one graph, with labels of 3 column names ("x", "y", "z").

I use the following code to plot, but don't know how to add labels

p <- ggplot() + 
   geom_line(aes(time, x), df, colour = "red") + 
   geom_line(aes(time, y), df, colour = "blue") + 
   geom_line(aes(time, z), df,colour = I("darkgreen")) + 
   xlab("Time") + ylab("value")

It is better to convert it to long format i.e. library(tidyverse);df %>% gather(key, val, -time) %>% ggplot(aes(x = time, y = val, color = key)) + geom_line() — akrun
– akrun, Commented Dec 19, 2017 at 5:48
I used the long version before, just wonder if there are any other ways of doing it as a wide format. Your code works perfectly~! — ys3006
– ys3006, Commented Dec 19, 2017 at 5:56
Just like you did, you can do it with the wide format. You may have to check for geom_label for the label — akrun
– akrun, Commented Dec 19, 2017 at 5:58
Couldn't figure it out, I was trying to label the lines by color as well by geom_label(label=colnames(df[,-1]), but no change to the existing plot. Thanks for the suggestions~! — ys3006
– ys3006, Commented Dec 19, 2017 at 6:38

f.lechleitner · Accepted Answer · 2017-12-19 07:20:27Z

2

Is this what you want?

ggplot(data = df) +
  geom_line(aes(time, x, color = "X")) +
  geom_line(aes(time, y, color = "Y")) +
  geom_line(aes(time, z, color = "Z")) +
  xlab("Time") +
  ylab("value") +
  labs(color = "YOUR LEGEND TITLE")

although @akrun is right, converting your data to long format would be the way to go here:

library(reshape2)
df <- melt(df, id.vars = "time")

> df
   time variable value
1     1        x     1
2     2        x     2
3     3        x     3
4     4        x     4
5     1        y     2
6     2        y     4
7     3        y     6
8     4        y     8
9     1        z     1
10    2        z     3
11    3        z     5
12    4        z     7

and then

ggplot(data = df, aes(x = time, y = value, color = variable)) +
  geom_line() +
  xlab("Time") +
  ylab("value") +
  labs(color = "YOUR LEGEND TITLE")

The legend-title is optional btw:

ggplot(data = df, aes(x = time, y = value, color = variable)) +
  geom_line() +
  xlab("Time") +
  ylab("value") +
  labs(color = "")

edited Dec 19, 2017 at 7:20

answered Dec 19, 2017 at 6:37

f.lechleitner

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7 Comments

ys3006 Over a year ago

Exactly~! I didn't know the labs() before, does it work like combining all colors with labels in each geom_lines(..., color = "labels")?

f.lechleitner Over a year ago

you don't really need the labs(color = "...") command, it only changes the title of the color legend. Can also be used for linetype or shape, etc. To get the labels to show up, I put the color inside the aes of geom_line, like geom_line(aes(color= ...)). If you put it outside the aes like so geom_line(aes(), color = ...) you only change the color of the line. I hope I understood your question correctly!

ys3006 Over a year ago

Long version does make more sense~ thank you so much for helping me, and recall the melt function, seems easier than gather, which I need to figure out the key and value.

ys3006 Over a year ago

I see... so color = "X" here color is actually automatically be given, and "X" is the way to label those systems generated colors, might be a way to understand this? haha, anyway, I think I am pretty clear of all the methods here, super helpful~

f.lechleitner Over a year ago

Yes the color is chosen automatically, although you can change it manually; check out this link: sthda.com/english/wiki/…

|

MKR · Accepted Answer · 2017-12-19 06:57:20Z

1

You can use scale_colour_manual to show the legend. The modified code will look like:

p <- ggplot(df, aes(x,y,z)) + 
  geom_line(aes(time, x, colour = "x")) + 
 geom_line(aes(time, y, colour = "y")) + 
 geom_line(aes(time, z,colour = "z")) + 
 scale_colour_manual("", 
                      breaks = c("x", "y", "z"),
                      values = c("red", "blue", "green")) +
 xlab("Time") + ylab("value")

answered Dec 19, 2017 at 6:57

MKR

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2 Comments

ys3006 Over a year ago

Hahaha, I was just thinking how to select the color manually rather than automatically be given the color. Tried your code, works perfectly~ Thx

MKR Over a year ago

@ys3006 Solution delivered beforehand. I knew that will be next thing you will be looking for.

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