Positive and negative bars

Draw bars from zero and color them according to their sign.

Every bar starts at zero. Red bars extend below the baseline and blue bars extend above it. A threshold color scale switches colors at zero.

Data use and provenance

NumPy creates 60 positions. GenomeSpy calculates the wave-shaped values in the browser. No source dataset is required.

Adapted from the official GenomeSpy example.

Code

"""Positive and negative bars.

Draw bars from zero and color them according to their sign.
"""

import numpy as np
import pandas as pd

import genome_spy as gs


data = pd.DataFrame({"x": np.arange(60)})
chart = (
    gs.Chart(data)
    .transform_calculate(y=gs.expr.sin((gs.datum.x - 30) / 4) + (gs.datum.x - 30) / 30)
    .mark_rect()
    .encode(
        x=gs.X("x:I").scale(padding=0.1),
        y=gs.Y("y:Q"),
        # A data-space zero makes every bar start at the same baseline.
        y2=gs.Y2({"datum": 0}),
        color=gs.Color("y:Q")
        .scale(type="threshold", domain=[0], range=["#ed553b", "#20639b"])
        .legend(None),
    )
)

Show generated specification