在 R 中绘制对数正态概率密度 [英] Plot Lognormal Probability Density in R

问题描述

我正在尝试为 R 中的对数正态概率密度生成一个图，其中包含 3 个不同的均值对数和标准差对数.我尝试了以下方法，但我的图表太丑了，一点也不好看.

 x<- seq(0,10,length = 100)a <- dlnorm(x, meanlog = 0, sdlog = 1, log = FALSE)b <- dlnorm(x, meanlog = 0, sdlog = 1.5, log = FALSE)g <- dlnorm(x, meanlog = 1.5, sdlog = 0.2, log = FALSE)情节(x，a，lty = 5，col =蓝色"，lwd = 3)线(x，b，lty = 2，col =红色")线(x，g，lty = 4，col =绿色")

我什至试图在每个平均日志和标准偏差日志的右上方添加图例，但它对我不起作用.我想知道是否有人可以指导我解决这个问题.

您还可以阅读 ?plotmath 以添加表达式.尝试将上面的 legend 参数更改为:

legend = c(expression(ln(y) %~% N(0,1)),表达式(ln(y) %~% N(0,1.5)),表达式(ln(y) %~% N(1.5,0.2)))

I am trying to generate a plot for Lognormal Probability Density in R, with 3 different means log and standards deviation log. I have tried the following, but my graph is so ugly and does not look good at all.

 x<- seq(0,10,length = 100)
 a <- dlnorm(x, meanlog = 0, sdlog = 1, log = FALSE)
 b <- dlnorm(x, meanlog = 0, sdlog = 1.5, log = FALSE)
 g <- dlnorm(x, meanlog = 1.5, sdlog = 0.2, log = FALSE)
 plot(x,a, lty=5, col="blue", lwd=3)
 lines(x,b, lty=2, col = "red")
 lines(x,g, lty=4, col = "green")

I even was trying to add legend on the right top for each mean log and standard deviation log, but it would not work with me. I was wondering if someone could guide me out with that.

Right top of the graph

解决方案

There is really nothing wrong in your code. You just forgot to:

• use type = "l" in plot;
• set a good ylim to hold all lines.

Here is a simple solution with matplot:

matplot(x, cbind(a,b,g), type = "l", ylab = "density", main = "log-normal",
        col = 1:3, lty = 1:3)

To add legend, use

legend("topright",
       legend = c("mu = 0, sd = 1", "mu = 0, sd = 1.5", "mu = 1.5, sd = 0.2"),
       col = 1:3,
       lty = 1:3)

You can also read ?plotmath for adding expressions. Try changing the legend argument above to:

legend = c(expression(ln(y) %~% N(0,1)),
           expression(ln(y) %~% N(0,1.5)),
           expression(ln(y) %~% N(1.5,0.2)))

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