图例在R图中落后

Question

I am generating a plot using the following sample code

x=seq(1,10, length=100)       
y=seq(-5,5,length=100)    
pdf("plot.pdf")   
plot(y~x, type="n", xlab="", ylab="")     
for(i in 1:4){   
y=rnorm(100, mean=i, sd=i)   
lines(x,y, type="l",lty=i)     
}   
legend("topright", legend=c("a", "b", "c"), lty=c(1,2,3,4), pch=c(1,2,3,4))   
dev.off()   

and when I save the plot in pdf, then the legend goes behind the drawn lines. While I want that the graphs should looks like the following while saving in the form of pdf.

Answer 1

As you're seeing, the background color for the legend defaults to "transparent" . To set it instead to an opaque "white" , use its bg parameter, like this:

legend("topright", legend=c("a", "b", "c"), lty=c(1,2,3,4), pch=c(1,2,3,4),
       bg = "white")

Answer 2

It's not on top, it's transparent. set the argument bg = 'white' in the legend command.