Add legend to a plot

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I have the data frame df, structured like this:

age salary graduate
19  22000  "no"
25  24000  "yes"
23  26000  "yes"
30  30000  "no"

I made the plot of the salary as a function of age, changing the color of the dot whether the person is a graduate or not in this way:

plot(df$age, df$salary, col=ifelse(df$graduate=="yes", "blue", "red"), pch=16, xlab="age", ylab="salary")

How can I add a legend titled "Graduate" with an explanation of the color of the dots (i.e. blue dot = graduate, red dot = not graduate)?

r
1 Answers

You can change the shape using pch see ?legend for more details

df <- data.frame(age=c(19,25,23,30),salary=c(22000,24000,26000,30000),graduate=c("no","yes","no","no"))

plot(df$age, df$salary, col=ifelse(df$graduate=="yes", "blue", "red"), pch=16, xlab="age", ylab="salary")
legend("topleft",pch=16, legend=c("Graduated", "Not Graduated"),
       col=c("blue", "red"), title="Graduated")

Output:

enter image description here

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