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pythonaltairvega-lite

Setting colors in Altair charts

I am trying to create a chart tracking 19 different columns of data and am looking to set a pre-defined color code for each different layer.

base = alt.Chart(historical_WTI.loc['0': '220'].reset_index(), 
                 title=f"WTI Futures (as of {last_date})").mark_line().encode(
    x = alt.X('days_to_expiry', title = 'Days to Expiry'),
    y = alt.Y(alt.repeat('layer'), scale=alt.Scale(zero = False), 
              type="quantitative", title = 'Open Interest'), 
    color = alt.Color('Key:O', scale = alt.Scale(domain = WTI_securities, range = color_list))
).repeat(layer = historical_WTI.columns.values.tolist())
base

WTI_securities and color_list are both lists that are in the order requried for my mapping but I am returned with the following chart

when I comment out the color line, I am able to get the following chart but I need the color mapping and legend.

anyone knows what I am doing wrong?

Solution

  • Don't know if this answers your question, but I started from this example:
    https://altair-viz.github.io/gallery/line_chart_with_color_datum.html
    adding the configure_range.

    import altair as alt
from vega_datasets import data

source = data.movies()

colors = ['#7fc97f','#beaed4','#fdc086']

alt.Chart(source).mark_line().encode(
    x=alt.X("IMDB_Rating", bin=True),
    y=alt.Y(
        alt.repeat("layer"), aggregate="mean", title="Mean of US and Worldwide Gross"
    ),
    color=alt.datum(alt.repeat("layer")),
).repeat(
    layer=["US_Gross", "Worldwide_Gross", "Production_Budget"],
).configure_range(
    category=alt.RangeScheme(colors)
)

    Which gives me this:
    plot