Why is "white" doesn't show as white?

[ma-sadeghi]

The following code snippet

temp = alt.Chart(source).mark_rect().encode(
    x=alt.X('x:O', sort=alt.EncodingSortField('y', order='descending')),
    y=alt.Y('y:O', sort=alt.EncodingSortField('y', order='descending')),
    color=alt.Color('z:Q', scale=alt.Scale(range=["white", "green"]))
).configure_scale(
    bandPaddingInner=0.1
)

produces the following heatmap:

Is there a way to force altair to show "white" as actual "white"?

[jakevdp]

If you want specific values to be exactly white (rather than just on a linear scale that starts at white), you can specify multiple domain and range values to create a piecewise linear scale. For example:

import altair as alt
import pandas as pd

x, y = np.meshgrid(range(-5, 5), range(-5, 5))
z = 20 * np.random.random(x.shape)
source = pd.DataFrame({'x': x.ravel(),
                       'y': y.ravel(),
                       'z': z.ravel()})


alt.Chart(source).mark_rect().encode(
    x=alt.X('x:O', sort=alt.EncodingSortField('y', order='descending')),
    y=alt.Y('y:O', sort=alt.EncodingSortField('y', order='descending')),
    color=alt.Color('z:Q', scale=alt.Scale(domain=[0, 2, 20], range=["white", "white", "green"]))
).configure_scale(
    bandPaddingInner=0.1
)

[joelostblom]

@ma-sadeghi I am going through Altair issues to find those that have been resolved and can be closed. It looks to me like this issue has been solved so I am closing it, but please feel free to reopen and add a comment if there is something you don't think is resolved yet.