| """ | |
| Stacked Density Estimates | |
| ------------------------- | |
| To plot a stacked graph of estimates, use a shared ``extent`` and a fixed | |
| number of subdivision ``steps`` to ensure that the points for each area align | |
| well. Density estimates of measurements for each iris flower feature are plot | |
| in a stacked method. In addition, setting ``counts`` to true multiplies the | |
| densities by the number of data points in each group, preserving proportional | |
| differences. | |
| """ | |
| # category: area charts | |
| import altair as alt | |
| from vega_datasets import data | |
| source = data.iris() | |
| alt.Chart(source).transform_fold( | |
| ['petalWidth', | |
| 'petalLength', | |
| 'sepalWidth', | |
| 'sepalLength'], | |
| as_ = ['Measurement_type', 'value'] | |
| ).transform_density( | |
| density='value', | |
| bandwidth=0.3, | |
| groupby=['Measurement_type'], | |
| extent= [0, 8], | |
| counts = True, | |
| steps=200 | |
| ).mark_area().encode( | |
| alt.X('value:Q'), | |
| alt.Y('density:Q', stack='zero'), | |
| alt.Color('Measurement_type:N') | |
| ).properties(width=400, height=100) | |