Matplotlib散点图与图例 [英] Matplotlib scatter plot with legend

问题描述

我想创建一个Matplotlib散点图，并用图例显示每个类的颜色.例如，我有一个x和y值的列表，以及一个classes值的列表. x，y和classes列表中的每个元素对应于图中的一个点.我希望每个类都具有自己的颜色(已经进行了编码)，但是然后我希望这些类在图例中显示.我应将什么参数传递给legend()函数以实现此目的?

I want to create a Matplotlib scatter plot, with a legend showing the colour for each class. For example, I have a list of x and y values, and a list of classes values. Each element in the x, y and classes lists corresponds to one point in the plot. I want each class to have its own colour, which I have already coded, but then I want the classes to be displayed in a legend. What paramaters do I pass to the legend() function to achieve this?

到目前为止，这是我的代码:

Here is my code so far:

x = [1, 3, 4, 6, 7, 9]
y = [0, 0, 5, 8, 8, 8]
classes = ['A', 'A', 'B', 'C', 'C', 'C']
colours = ['r', 'r', 'b', 'g', 'g', 'g']
plt.scatter(x, y, c=colours)

推荐答案

首先，我觉得您在声明颜色时应该使用撇号，而不是反引号.

First, I have a feeling you meant to use apostrophes, not backticks when declaring colours.

对于图例，您需要一些形状以及类.例如，下面为class_colours中的每种颜色创建一个称为recs的矩形的列表.

For a legend you need some shapes as well as the classes. For example, the following creates a list of rectangles called recs for each colour in class_colours.

import matplotlib.patches as mpatches

classes = ['A','B','C']
class_colours = ['r','b','g']
recs = []
for i in range(0,len(class_colours)):
    recs.append(mpatches.Rectangle((0,0),1,1,fc=class_colours[i]))
plt.legend(recs,classes,loc=4)

如果需要，您也可以使用圆圈，只需查看matplotlib.patches文档即可.还有第二种创建图例的方法，其中，您可以为每个点使用单独的散点命令为一组点指定标签".下面是一个示例.

You could use circles too if you wanted, just check out the matplotlib.patches documentation. There is a second way of creating a legend, in which you specify the "Label" for a set of points using a separate scatter command for each set. An example of this is given below.

classes = ['A','A','B','C','C','C']
colours = ['r','r','b','g','g','g']
for (i,cla) in enumerate(set(classes)):
    xc = [p for (j,p) in enumerate(x) if classes[j]==cla]
    yc = [p for (j,p) in enumerate(y) if classes[j]==cla]
    cols = [c for (j,c) in enumerate(colours) if classes[j]==cla]
    plt.scatter(xc,yc,c=cols,label=cla)
plt.legend(loc=4)

第一种方法是我个人使用的方法，第二种方法是我在查看matplotlib文档时才发现的.由于图例覆盖了数据点，因此我将它们移动了，并且可以在此处找到图例的位置.如果还有另一种制作图例的方法，则在文档中进行了几次快速搜索后，我无法找到它.

The first method is the one I've personally used, the second I just found looking at the matplotlib documentation. Since the legends were covering datapoints I moved them, and the locations for legends can be found here. If there's another way to make a legend, I wasn't able to find it after a few quick searches in the docs.

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