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"""
Normalized Parallel Coordinates Example
---------------------------------------
A `Parallel Coordinates <https://en.wikipedia.org/wiki/Parallel_coordinates>`_
chart is a chart that lets you visualize the individual data points by drawing
a single line for each of them.
Such a chart can be created in Altair by first transforming the data into a
suitable representation.
This example shows a modified parallel coordinates chart with the Iris dataset,
where the y-axis shows the value after min-max rather than the raw value. It's a
simplified Altair version of `the VegaLite version <https://vega.github.io/vega-lite/examples/parallel_coordinate.html>`_
"""
# category: other charts
import altair as alt
from vega_datasets import data
from altair import datum
source = data.iris()
alt.Chart(source).transform_window(
index='count()'
).transform_fold(
['petalLength', 'petalWidth', 'sepalLength', 'sepalWidth']
).transform_joinaggregate(
min='min(value)',
max='max(value)',
groupby=['key']
).transform_calculate(
minmax_value=(datum.value-datum.min)/(datum.max-datum.min),
mid=(datum.min+datum.max)/2
).mark_line().encode(
x='key:N',
y='minmax_value:Q',
color='species:N',
detail='index:N',
opacity=alt.value(0.5)
).properties(width=500)
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