Altair: Change tick/label spacing

[ghost]

I am creating a mark_line chart and my data results in the x axis from 0-30, with the labels/ticks every 2 (0,2,4,6, etc....). I would like to change the labels/ticks to every 5 instead (0,5,10, etc.). Is there a convenient way to accomplish this?

Thank you in advance or the help!

[jakevdp]

Ticks are controlled via the axis property of encodings. So, for example, you can explicitly set tick locations using the values setting:

import altair as alt
import pandas as pd

df = pd.DataFrame({
    'x': range(20),
    'y': range(20)
})

alt.Chart(df).mark_line().encode(
    alt.X('x', axis=alt.Axis(values=[0, 5, 10, 15, 20])),
    alt.Y('y')
)

The full set of axis properties is documented here: https://altair-viz.github.io/user_guide/generated/core/altair.Axis.html The tickMinStep property might be useful if you don't want to specify the values explicitly, but want the minimum step to be larger.

[ghost]

Thank you, that works perfectly.

Much appreciated!

[firasm]

Is there a way to set the tick frequency for Ordinal data?

Adapted the above for a mark_rect() example:

Desired output: every 5th tick (for example)

import altair as alt
import pandas as pd

df = pd.DataFrame({
    'x': range(20),
    'y': range(20)
})

alt.Chart(df).mark_rect().encode(
    alt.X('y:O',
          axis=alt.Axis(tickMinStep = 2, labelAngle=0),

),
    alt.Y('x:Q', axis=alt.Axis(values=[0, 5, 10, 15, 20])),
    alt.Color('x:Q'),
    tooltip=['x','y']
)

[jakevdp]

tickMinStep and the like only apply to quantitative scales. For ordinal or categorical scales, you can specify values directly:

alt.Chart(df).mark_rect().encode(
    alt.X('x:O', axis=alt.Axis(values=list(range(1, 20, 2)))),
    alt.Y('y:Q'),
    alt.Color('x:Q'),
    tooltip=['x','y']
)

Note also that if necessary, the renderer will automatically adjust tick labels to prevent overlap:

df = pd.DataFrame({
    'x': range(50),
    'y': range(50)
})

alt.Chart(df).mark_rect().encode(
    alt.X('x:O'),
    alt.Y('y:Q'),
    alt.Color('x:Q'),
    tooltip=['x','y']
).properties(width=400)