问使用“直接标签”包标出选择曲线

EN

    require("ggplot2")
    require("reshape2")
    require("directlabels")

    # Test function
    f <- function(x,y){
    x^2 + y^2
    }

    # Define range of values for each variable
    X <- seq(-4,4,0.1)
    Y <- seq(0,4,2)

    ## Label all curves:
    # Create data frame
    M <- lapply(Y, f, X)
    names(M) = Y

    M <- melt(M, id.vars = "Y")
    M <- cbind(M,X)
    names(M) = c("value", "Y", "X")

    # Plot (x, f(x,y)) for each value of y.
    p <- ggplot(M, aes(x = X, y = M$value)) + 
    geom_line(aes(y = M$value, color = M$Y), group = M$Y)
    p <- p + geom_dl(aes(label = M$Y),  method = "top.bumpup")
    p