使用ggplot无法在散点图顶部生成多边形 [英] Trouble producing a polygon on top of a scatterplot using ggplot

问题描述

目前，我正尝试将我的图形知识从R中的 plot 函数转换为 ggplot 函数。我已经开始为给定的数据集构造散点图和相应的图例，但是我想使用 ggplot 将函数 geom_polygon 合并到我的图中$ C>。

具体来说，我想从散点图的原点捕捉一个三角形区域。为了再现性，假设我有以下数据集：

pre $ rawdata <-data.frame（matrix（c（1,1， 1，
2,1，-1，
3，-1，-1，
4，-1,1，
4，-2,2），5， 3，byrow = TRUE））
名称（rawdata）< -c（Town，x.coordinate，y.coordinate）
rawdata [，1]<因子（rawdata [，1]）$ ​​b $ b

为了构造散点图和图例，我被告知要做到以下几点：

  p1 <-ggplot（data = rawdata，aes（x = x.coordinate，y = y。坐标，颜色=城镇，形状=城镇））
 + theme_bw（）+ geom_point（）
  

结果如下：
点击此处。

我现在想要做的是产生一个多边形。为此，我构建了以下数据框以用于 geom_polygon 函数中：

  geom_polygon（data = polygondata，aes（x = xa，y = ya），color =darkslategray2，
 fill =darkslategray2，alpha = 0.25）
  

然而，当我将它与 p1 结合时，出现以下错误：

  eval中的错误（expr，envir，enclos）：object'Town'not found 
  

从一些混乱中，我注意到当我省略形参数时， ggplot 函数，我可以很容易地生成所需的输出，如图所示这里。然而，我希望为美学保持形状。

我也会遇到类似的问题，当我尝试生成连接箭头散点图使用 ggplot 。但是，我会在解决这个问题之后，因为根本问题可能在这里。

解决方案

将以下内容添加到 polygondata ：

  polygondata $ Town = NA 
  

即使你没有在 geom_polygon 中使用这个变量，ggplot希望它在那里如果该列在ggplot的主要调用中用于审美。

或者，如果您将初始绘图中的美学贴图移至 geom_point ，则可以避免该错误比主ggplot调用，像这样：

  p1 < -  ggplot（data = rawdata）+ 
 theme_bw（ ）+ 
 geom_point（aes（x = x.coordinate，y = y.coordinate，color = Town，shape = Town））
  

在这种情况下，您不需要为 polygondata 小镇列c>。

Currently, I am trying to transition my graphical knowledge from the plot function in R, to the ggplot function. I have began constructing scatterplots and corresponding legends for a given data set, however I want to incorporate the function geom_polygon onto my plots using ggplot.

Specifically, I want to capture a triangular region from the origin of a scatterplot. For reproducibility, say I have the following data set:

rawdata<-data.frame(matrix(c(1,1,1,
                         2,1,-1,
                         3,-1,-1,
                         4,-1,1,
                         4,-2,2),5,3,byrow=TRUE))
names(rawdata)<-c("Town","x.coordinate","y.coordinate")
rawdata[,1]<-as.factor(rawdata[,1])

To construct a scatterplot along with a legend, I have been told to do the following:

p1<-ggplot(data=rawdata,aes(x=x.coordinate,y=y.coordinate,colour=Town,shape=Town)) 
+ theme_bw() + geom_point()  

The result is the following: Click here.

What I want to do now is produce a polygon. To do so, I have construct the following dataframe to use in the geom_polygon function:

geom_polygon(data=polygondata,aes(x = xa, y = ya),colour="darkslategray2",
             fill = "darkslategray2",alpha=0.25)

However, when I combine this with p1, I get the following error:

Error in eval(expr, envir, enclos) : object 'Town' not found

From some messing around, I have noticed that when I omit the shape argument from the ggplot function, I can easily produce the desired output which is shown here. However, I wish to keep the shape for aesthetics.

I also get a similar problem when I try to produce arrows which connect points on the scatterplot using ggplot. However, I will address this problem after, as the root problem may be here.

解决方案

Add the following to polygondata:

polygondata$Town = NA

Even though you're not using that variable in geom_polygon, ggplot expects it to be there if that column is used for an aesthetic in the main call to ggplot.

Alternatively, I think you could avoid the error if you move the aesthetic mapping in the initial plot to geom_point rather than the main ggplot call, like this:

p1 <- ggplot(data=rawdata) + 
        theme_bw() + 
        geom_point(aes(x=x.coordinate, y=y.coordinate, colour=Town, shape=Town)) 

In that case, you wouldn't need to add a Town column to polygondata.

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