Add padding between far left-most bar and y-axis

Question

I would like to add padding between the far left-most bar (A) from x-axis and y-axis of Bar plot using Altair Python. I am using Python V.3.8 and altair V.4.2.0.

I am new to Altair so I am experiment with the examples provided in the altair documentation so here is a an example snippet code from their docs (https://altair-viz.github.io/gallery/simple_bar_chart.html):

import altair as alt
import pandas as pd

source = pd.DataFrame({
    'a': ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I'],
    'b': [28, 55, 43, 91, 81, 53, 19, 87, 52]
})

alt.Chart(source).mark_bar().encode(
    x='a',
    y='b'
)

I want to add padding or space between element A from x-axis and the y-axis. Also I would like introduce padding from the bottom of x-axis which will lift all the bars a bit to the top.

I tried the following but nothing change:

import altair as alt
import pandas as pd

source = pd.DataFrame({
    'a': ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I'],
    'b': [28, 55, 43, 91, 81, 53, 19, 87, 52]
})

alt.Chart(source).mark_bar().encode(
    x=alt.X("a", axis=alt.Axis(tickSize=7, titlePadding=10, tickColor="black", labelPadding=6, domainWidth=1.7,domainCap="round", domainColor='black')
    y=alt.Y("b", axis=alt.Axis(tickSize=7, titlePadding=10, tickColor="black", labelPadding=6, domainWidth=1.7,domainCap="round", domainColor='black')
)

How do I do introduce padding in both axises as described above ?

Thank you so much in advance.

Answer 1

Simply shifting the axis can be done by adding an offset value to the intended one.

import altair as alt
import pandas as pd
import numpy as np

source = pd.DataFrame({
    'a': ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I'],
    'b': [28, 55, 43, 91, 81, 53, 19, 87, 52]
})

alt.Chart(source).mark_bar().encode(
  x=alt.X('a', axis=alt.Axis(offset=10)),
  y=alt.Y('b', axis=alt.Axis(offset=10))
)

To lift the graph

The width of the bar and the range of the y-axis are adjusted.

alt.Chart(source).mark_bar(size=10).encode(
  x=alt.X('a', scale=alt.Scale(domainMin=-5, padding=3)),
  y=alt.Y('b', scale=alt.Scale(domainMin=-5, padding=3))
)