如何将bokeh vbar chart参数与groupby对象一起使用? | chart参数与groupby对象一起使用

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问题描述

问题

以下代码来自bokeh文档中的分组vbar图表示例.在这个例子中我有些不明白.

Below code is grouped vbar chart example from bokeh documentation.There are something i can't understand on this example.

"cyl_mfr"来自于factor_cmap()和vbar()中?

Where 'cyl_mfr' is come from in factor_cmap() and vbar()?

'mpg_mean'，它是否在计算'mpg'列的平均值?如果那样的话为什么"mpg_sum"不起作用?

'mpg_mean' , is it calculating the mean of 'mpg' column? if then, why 'mpg_sum' doesn't work?

我想像这样的例子制作自己的vbar图表.

I want to make my own vbar chart like this example.

代码

from bokeh.io import show, output_file
from bokeh.models import ColumnDataSource, HoverTool
from bokeh.plotting import figure
from bokeh.palettes import Spectral5
from bokeh.sampledata.autompg import autompg_clean as df
from bokeh.transform import factor_cmap

output_file("bars.html")

df.cyl = df.cyl.astype(str)
df.yr = df.yr.astype(str)

group = df.groupby(('cyl', 'mfr'))

source = ColumnDataSource(group)
index_cmap = factor_cmap('cyl_mfr', palette=Spectral5,
factors=sorted(df.cyl.unique()), end=1)

p = figure(plot_width=800, plot_height=300, title="Mean MPG by # Cylinders
           and Manufacturer",
           x_range=group, toolbar_location=None, tools="")

p.vbar(x='cyl_mfr', top='mpg_mean', width=1, source=source,
       line_color="white", fill_color=index_cmap, )

p.y_range.start = 0
p.x_range.range_padding = 0.05
p.xgrid.grid_line_color = None
p.xaxis.axis_label = "Manufacturer grouped by # Cylinders"
p.xaxis.major_label_orientation = 1.2
p.outline_line_color = None

p.add_tools(HoverTool(tooltips=[("MPG", "@mpg_mean"), ("Cyl, Mfr",
            "@cyl_mfr")]))

show(p)

推荐答案

group = df.groupby(('cyl', 'mfr'))产生<pandas.core.groupby.DataFrameGroupBy object at 0x0xxx>.如果将其传递给ColumnDataSource，则bokeh会产生很多魔力，并且已经计算出很多统计数据

The group = df.groupby(('cyl', 'mfr')) makes a <pandas.core.groupby.DataFrameGroupBy object at 0x0xxx>. If you pass this to a ColumnDataSource, bokeh does a lot of magic, and calculates a lot of statistics already

df.columns

Index(['mpg', 'cyl', 'displ', 'hp', 'weight', 'accel', 'yr', 'origin', 'name', 'mfr'],

source.column_names

cyl_mfr是您按串联分组的2列的标签.在source中，它已成为一列元组

the cyl_mfr is the labels of the 2 columns on which you grouped by concatenated. In source this has become a column of tuples

mpg_sum未计算.如果您不能计算总和，则需要自己计算.

mpg_sum is not calculated. If you cant the sum, you will need to calculate that yourself.

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