使用ggplot将图例添加到单个折线图 [英] Adding legend to a single line chart using ggplot

问题描述

I just try to make a line chart and add a legend to it using ggplot in R. The following is my code.

c> ggplot（mtcars，aes（x = mpg，y = wt））+ geom_line（stat =identity）+ scale_fill_identity（name =，guide =legend，labels = c（myLegend））

ggplot(mtcars, aes(x=mpg, y=wt)) + geom_line(stat = "identity") + scale_fill_identity(name = "", guide = "legend", labels = c("myLegend"))

我得到以下结果：

and I got the following:

图中没有显示图例，我想要的是以下内容：

The legend is not shown in the plot and what I want is the following:

我使用Matlab绘图。有谁能告诉我如何在R中做到这一点？非常感谢你！

which I plot using Matlab. Could anyone tell me how to do it in R? Thank you so much!!

推荐答案

你的绘图并没有显示图例，因为没有美学映射到这一行。基本上，ggplot没有理由添加图例，因为只有一行。

You plot is not showing a legend, because there are no aesthetics mapped to the line. Basically, ggplot sees no reason to add a legend as there's only one line.

获取图例的简单方法是将行类型映射为字符串：

A simple way to get a legend is to map the line type to a character string:

ggplot(mtcars, aes(x=mpg, y=wt, lty = 'MyLegend')) + geom_line()

您可以看看？scale_linetype ，以获取有关如何修改tthat图例的信息。

You can have a look at ?scale_linetype for information on how to modify tthat legend.

例如，使用 + scale_linetype（'MyLegendTitle'）更改图例标题。

For example, use + scale_linetype('MyLegendTitle') to change the legend title.

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