[英]Appending sample number to X-Labels in altair
I would like to automatically append the sample # (in parentheses) corresponding to the x-labels of an altair figure.我想自动 append 样本#(在括号中)对应于 altair 图形的 x-labels。 I am open to doing this outside of altair, but I thought there may be a way to do it at the figure level using altair/vega-lite.我愿意在 altair 之外执行此操作,但我认为可能有一种方法可以使用 altair/vega-lite 在图形级别执行此操作。 I am pasting the code using an example from the altair/vega website (part of the vega_dataset), but with a hackneyed, manual method in which I rename the labels explicitly for one of the labels.我正在使用来自 altair/vega 网站(vega_dataset 的一部分)的示例粘贴代码,但使用了一种陈旧的手动方法,在该方法中,我为其中一个标签显式地重命名了标签。 In this case, I have added the sample number of 73 to Europe.在这种情况下,我已将样本编号 73 添加到欧洲。
import altair as alt
from vega_datasets import data
df = data.cars()
df['Origin'] = df['Origin'].replace({'Europe':'Europe (n=73)'})
alt.Chart(df).transform_density(
'Miles_per_Gallon',
as_=['Miles_per_Gallon', 'density'],
extent=[5, 50],
groupby=['Origin']
).mark_area(orient='horizontal').encode(
y='Miles_per_Gallon:Q',
color='Origin:N',
x=alt.X(
'density:Q',
stack='center',
impute=None,
title=None,
axis=alt.Axis(labels=False, values=[0],grid=False, ticks=True),
),
column=alt.Column(
'Origin:N',
header=alt.Header(
titleOrient='bottom',
labelOrient='bottom',
labelPadding=0,
),
)
).properties(
width=100
).configure_facet(
spacing=0
).configure_view(
stroke=None
)
You could use pandas to generate the replacement dictionary and assign it to a new dataframe column:您可以使用 pandas 生成替换字典并将其分配给新的 dataframe 列:
import altair as alt
from vega_datasets import data
df = data.cars()
group_sizes = df.groupby('Origin').size()
replace_dict = group_sizes.index + ' (n=' + group_sizes.astype(str) + ')'
df['Origin_with_count'] = df['Origin'].replace(replace_dict)
alt.Chart(df).transform_density(
'Miles_per_Gallon',
as_=['Miles_per_Gallon', 'density'],
extent=[5, 50],
groupby=['Origin_with_count', 'Origin']
).mark_area(orient='horizontal').encode(
y='Miles_per_Gallon:Q',
color='Origin:N',
x=alt.X(
'density:Q',
stack='center',
impute=None,
title=None,
axis=alt.Axis(labels=False, values=[0],grid=False, ticks=True),
),
column=alt.Column(
'Origin_with_count:N',
header=alt.Header(
title=None,
labelOrient='bottom',
labelPadding=0,
),
)
).properties(
width=100
).configure_facet(
spacing=0
).configure_view(
stroke=None
)
You might be able to do something more elegant with labelExpr
, not sure.不确定,您也许可以使用labelExpr
做一些更优雅的事情。
You could overlay a text mark with the count instead.您可以用计数覆盖文本标记。
I was able to do this with the following code.我能够使用以下代码做到这一点。 I was not able to manage the y position of the text (see commented-out line) or use the n datum in the header labelExpr for some reason.由于某种原因,我无法管理文本的 y position(参见注释掉的行)或使用 header labelExpr 中的 n 数据。
df = data.cars()
violin = alt.Chart(df).transform_density(
'Miles_per_Gallon',
as_=['Miles_per_Gallon', 'density'],
extent=[5, 50],
groupby=['Origin']
).mark_area(orient='horizontal').encode(
y='Miles_per_Gallon:Q',
color='Origin:N',
x=alt.X(
'density:Q',
stack='center',
impute=None,
title=None,
axis=alt.Axis(labels=False, values=[0],grid=False, ticks=True),
),
).properties(width=100)
text = alt.Chart(df).mark_text().transform_aggregate(
cnt='count()',
groupby=["Origin"]
).transform_calculate(
n = "'n=' + datum.cnt",
).encode(
# y=alt.Y('mean(Miles_per_Gallon):Q'),
text=alt.Text('n:N'),
)
(violin + text).facet(
column=alt.Column('Origin:N'),
).configure_header(
labelExpr="[datum.value, datum.n]",
)
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