Add Legend to Ggplot2 Line Plot

Add legend to ggplot2 line plot

I tend to find that if I'm specifying individual colours in multiple geom's, I'm doing it wrong. Here's how I would plot your data:

##Subset the necessary columns
dd_sub = datos[,c(20, 2,3,5)]
##Then rearrange your data frame
library(reshape2)
dd = melt(dd_sub, id=c("fecha"))

All that's left is a simple ggplot command:

ggplot(dd) + geom_line(aes(x=fecha, y=value, colour=variable)) +
  scale_colour_manual(values=c("red","green","blue"))

Example plot

Add legend to geom_line() graph in r

ggplot needs aes to make a legend, moving colour inside aes(...) will build a legend automatically. then we can adjust the labels-colors pairing via scale_color_manual:

ggplot()+
  geom_line(data=Summary,aes(y=Y1,x= X,colour="Y1"),size=1 )+
  geom_line(data=Summary,aes(y=Y2,x= X,colour="Y2"),size=1) +
  scale_color_manual(name = "Y series", values = c("Y1" = "darkblue", "Y2" = "red"))

How to add a legend manually for line chart

The neatest way to do it I think is to add colour = "[label]" into the aes() section of geom_line() then put the manual assigning of a colour into scale_colour_manual() here's an example from mtcars (apologies that it uses stat_summary instead of geom_line but does the same trick):

library(tidyverse)

mtcars %>% 
  ggplot(aes(gear, mpg, fill = factor(cyl))) +
  stat_summary(geom = "bar", fun = mean, position = "dodge") +
  stat_summary(geom = "line", 
               fun = mean, 
               size  = 3, 
               aes(colour = "Overall mean", group = 1)) +
  scale_fill_discrete("") +
  scale_colour_manual("", values = "black")

^{Created on 2020-12-08 by the reprex package (v0.3.0)}

The limitation here is that the colour and fill legends are necessarily separate. Removing labels (blank titles in both scale_ calls) doesn't them split them up by legend title.

In your code you would probably want then:

...
ggplot(data = impact_end_Current_yr_m_actual, aes(x = month, y = gender_value)) + 
    geom_col(aes(fill = gender))+
    geom_line(data = impact_end_Current_yr_m_plan, 
              aes(x=month, y= gender_value, group=1, color="Plan"), 
              size=1.2)+
    scale_color_manual(values = "#288D55") +
...

(but I cant test on your data so not sure if it works)

How to add legend to ggplot2 line with point plot?

An automatic legend is only drawn if you map a variable on the color aesthetic. In your case map Condition on color and set colors manually. Try this:

    ggplot(mapping = aes(Date, LAI, color = Condition, linetype = Condition, shape = Condition))+
  geom_point(data=subset(X0_40cm, Condition=="Measured"))+
  geom_line(data=subset(X0_40cm, Condition=="Simulated"))+
  scale_color_manual(values = c("red", "black")) +
  scale_linetype_manual(values=c(NA,1)) +
  scale_shape_manual(values=c(16,NA)) +
  theme(legend.position=c(0.85,0.80))+
  scale_y_continuous(limits = c(0,3)) +
  labs(title="Winter wheat of I plot",y="LAI",x="Date")
  theme_update(plot.title=element_text(hjust=0.5))

Create legend for line chart R GGPlot2

It might help if you put your data into "long" form, such as this for your data frame graphDF (perhaps using pivot_longer from tidyr if necessary):

library(tidyr)

graphDF_long <- pivot_longer(data = graphDF, 
                             cols = c(noCVErr, CVErr), 
                             names_to = "model", 
                             values_to = "errRate")

This creates a new data.frame called graphDF_long that has a single column for the error rate, and a new column that specifies model:

      ks kAxis noCVAcc CVAcc model   errRate
   <int> <dbl>   <dbl> <dbl> <chr>     <dbl>
 1     1 1       1     0.828 noCVErr  0     
 2     1 1       1     0.828 CVErr    0.172 
 3     3 0.333   0.935 0.834 noCVErr  0.0655
 4     3 0.333   0.935 0.834 CVErr    0.166 
 5     5 0.2     0.881 0.816 noCVErr  0.119 
 6     5 0.2     0.881 0.816 CVErr    0.184 
 ....

Then, you can simplify your ggplot statement, and use an aesthetic with the column model for color:

library(ggplot2)

ggplot(data = graphDF_long, aes(x = rev(kAxis), y = rev(errRate), color = model)) +
  geom_line() +
  geom_point() +
  scale_color_manual(values = c("blue", "red"), 
                     labels = c("Cross Validation", "No Cross Validation")) +
  ylim(min(graphDF_long$errRate), max(graphDF_long$errRate)) +
  ggtitle("The KNN Error Rate for Cross Validated and Non-Cross Validated Models") +
  labs(y="Error Rate", x = "1/K")

This will generate the legend automatically:

Add legend to ggplot2 line with point plot

I would approach this problem in two steps.

Generally, to get stuff in the guides, ggplot2 wants you to put "aesthetics" like colour inside the aes() function. I typically do this inside the ggplot() rather than individually for each "geom", especially if everything kind of makes sense in a single dataframe.

My first step would be to remake your dataframe slightly. I would use the package tidyr (part of the tidyverse, like ggplot2, which is really nice for reformatting data and worth learning as you go), and do something like this

#key is the new variable that will be your color variable
#value is the numbers that had been in V2 and V3 that will now be your y-values
data_p %>% tidyr::gather (key = "color", value = "yval", V2, V3) 

#now, I would rewrite your plot slightly
P<-(newdf %>% ggplot(aes(x=V1,y=yval, colour=color))

#when you put the ggplot inside parentheses, 
#you can add each new layer on its own line, starting with the "+"
                 + geom_point()
                 + geom_line()
                 + scale_color_manual(values=c("#56B4E9","#009E73"))

#theme classic is my preferred look in ggplot, usually
                 + theme_classic()
)

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