如何使用Altair显示百分比直方图而不是计数 [英] How to show a histogram of percentages instead of counts using Altair
问题描述
如何使用Altair和Pandas获取总百分比的直方图,而不是计数的直方图?
我现在有这个:
我这样做的目的是
d = {'age':['12','32','43','54','32','32', '12']}
dfTest = pd.DataFrame(data = d)
alt.Chart(dfTest).mark_bar()。encode(
alt.X( age :Q,bin = True),
y ='count()',
)
您可以使用
编辑:这是我最初的答案,则要复杂得多:
这并不完全简单,因为它需要手动指定当前编码所隐含的bin和合计转换,然后再进行一次计算转换来计算百分比。下面是一个示例:
将熊猫作为pd
导入altair作为alt
来源= pd.DataFrame({'age':['12','32','43','54','32','32','12']})
alt .chart(source).transform_bin(
['age_min','age_max'],
field ='age',
).transform_aggregate(
count ='count() ',
groupby = ['age_min','age_max']
).transform_joinaggregate(
total ='sum(count)'
).transform_calculate(
pct ='datum.count / datum.total'
).mark_bar()。encode(
alt.X( age_min:Q,bin ='binned'),
x2 =' age_max',
y = alt.Y('pct:Q',axis = alt.Axis(format ='%'))
)
我希望我们能将来可以简化转换API。
How do I get a histogram of percentages of total instead of a histogram of count using Altair and Pandas?
I have this at the moment:
Which I got by doing this:
d = {'age': ['12', '32', '43', '54', '32', '32', '12']}
dfTest = pd.DataFrame(data=d)
alt.Chart(dfTest).mark_bar().encode(
alt.X("age:Q", bin=True),
y='count()',
)
You can do this with a Join Aggregate transform followed by a Calculate transform:
import pandas as pd
import altair as alt
source = pd.DataFrame({'age': ['12', '32', '43', '54', '32', '32', '12']})
alt.Chart(source).transform_joinaggregate(
total='count(*)'
).transform_calculate(
pct='1 / datum.total'
).mark_bar().encode(
alt.X('age:Q', bin=True),
alt.Y('sum(pct):Q', axis=alt.Axis(format='%'))
)
Edit: this was my initial answer, which is much more complicated:
It's not entirely straightforward, because it requires manually specifying the bin and aggregate transforms currently implied by your encoding, followed by a calculate transform to compute the percentages. Here is an example:
import pandas as pd
import altair as alt
source = pd.DataFrame({'age': ['12', '32', '43', '54', '32', '32', '12']})
alt.Chart(source).transform_bin(
['age_min', 'age_max'],
field='age',
).transform_aggregate(
count='count()',
groupby=['age_min', 'age_max']
).transform_joinaggregate(
total='sum(count)'
).transform_calculate(
pct='datum.count / datum.total'
).mark_bar().encode(
alt.X("age_min:Q", bin='binned'),
x2='age_max',
y=alt.Y('pct:Q', axis=alt.Axis(format='%'))
)
I'm hoping that we'll be able to streamline the transform API in the future.
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