如何在 R 中为绘图添加图例

Question

I´m new to R. I cannot put a legend in a plot chart, there is someting wrong with my code, I´ve tried to put a legend on this plot. I did a hash to put some colors on my model, but now I can´t figure out how to put the correct legend on it. This is what I di:

myhash<-c(a="green",b="pink",c="blue",d="purple",e="orange",f="brown",g="yellow",
          h="black",i="gray") 
mycolor<-myhash[df$category]
plot(df$growth,df$tannin,col=mycolor,cex=1,pch=16,xlab="Crecimiento",ylab="Taninos", main = "Modelo lineal Taninos vs Crecimiento")

I tried to put the legend like this :

legend("topright",c(df$tannin),fill=c("green","pink","blue","purple","orange","brown","yellow",
          "black","gray"))

Please let me know how can I fix it, Im very beginner in R. Also, I cannot use any library. Thanks in advance.

Answer 1

The problem seems to be that there is no legend (the argument to function legend , not the function) to show as text beside the fill colors.
To use a named argument, legend = unique(names(mycolor)) solves the problem.

set.seed(2020)
df <- data.frame(category = rep(c("a","b", "c", "d"), 4),
                 growth = 1:16, tannin = cumsum(rnorm(16)))

myhash <- c(a = "green", b = "pink", c = "blue", d = "purple") 
mycolor <- myhash[df$category]

plot(df$growth, df$tannin, col = mycolor, cex = 1, pch = 16,
     xlab = "Crecimiento", ylab = "Taninos", 
     main = "Modelo lineal Taninos vs Crecimiento")

legend("topright", legend = unique(names(mycolor)), fill = mycolor)