pandas 熊猫中按类别的散点图
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scatter plot by category in pandas
提问by jason adams
This has been troubling me for the past 30 minutes. What I'd like to do is to scatter plot by category. I took a look at the documentation, but I haven't been able to find the answer there. I looked here, but when I ran that in iPython Notebook, I don't get anything.
在过去的 30 分钟里，这一直困扰着我。我想做的是按类别散点图。我查看了文档，但我无法在那里找到答案。我看了这里，但是当我在 iPython Notebook 中运行它时，我什么也没得到。
Here's my data frame:
这是我的数据框：
time cpu wait category
8 1 0.5 a
9 2 0.2 a
2 3 0.1 b
10 4 0.7 c
3 5 0.2 c
5 6 0.8 b
Ideally, I'd like to have a scatter plot that shows CPU on the x axis, wait on the y axis, and each point on the graph is distinguished by category. So for example, if a=red, b=blue, and c=green then point (1, 0.5) and (2, 0.2) should be red, (3, 0.1) and (6, 0.8) should be blue, etc.
理想情况下，我想要一个散点图，在 x 轴上显示 CPU，在 y 轴上等待，并且图表上的每个点都按类别进行区分。例如，如果 a=red, b=blue, and c=green 那么点 (1, 0.5) 和 (2, 0.2) 应该是红色，(3, 0.1) 和 (6, 0.8) 应该是蓝色等等.
How would I do this with pandas? or matplotlib? whichever does the job.
我将如何用Pandas做到这一点？或matplotlib？无论哪个工作。
采纳答案by Alexander
This is essentially the same answer as @JoeCondron, but a two liner:
这与@JoeCondron 的答案基本相同，但有两个班轮：
cmap = {'a': 'red', 'b': 'blue', 'c': 'yellow'}
df.plot(x='cpu', y='wait', kind='scatter',
colors=[cmap.get(c, 'black') for c in df.category])
If no color is mapped for the category, it defaults to black.
如果没有为类别映射颜色，则默认为黑色。
EDIT:
编辑：
The above works for Pandas 0.14.1. For 0.16.2, 'colors' needs to be changed to 'c':
以上适用于 Pandas 0.14.1。对于 0.16.2，'colors' 需要更改为 'c'：
df.plot(x='cpu', y='wait', kind='scatter',
c=[cmap.get(c, 'black') for c in df.category])
回答by JoeCondron
You could do
你可以做
color_map = {'a': 'r', 'b': 'b', 'c': 'y'}
ax = plt.subplot()
x, y = df.cpu, df.wait
colors = df.category.map(color_map)
ax.scatter(x, y, color=colors)
This will give you red for category a, blue for b, yellow for c. So you can past a list of color aliases of the same length as the arrays. You can check out the myriad available colours here : http://matplotlib.org/api/colors_api.html. I don't think the plot method is very useful for scatter plots.
这将为您提供 a 类红色，b 类蓝色，c 类黄色。因此，您可以传递与数组长度相同的颜色别名列表。您可以在此处查看无数可用的颜色：http: //matplotlib.org/api/colors_api.html。我不认为 plot 方法对散点图很有用。
回答by alex314159
I'd create a column with your colors based on category, then do the following, where ax is a matplotlib ax and df is your dataframe:
我会根据类别用您的颜色创建一个列，然后执行以下操作，其中 ax 是 matplotlib ax， df 是您的数据框：
ax.scatter(df['cpu'], df['wait'], marker = '.', c = df['colors'], s = 100)
