Error Bars with Confidence Interval

This example shows how to show error bars using confidence intervals. The confidence intervals are computed internally in vega by a non-parametric bootstrap of the mean.

Method syntax

import altair as alt
from vega_datasets import data

source = data.barley()

error_bars = alt.Chart(source).mark_errorbar(extent='ci').encode(
  alt.X('yield').scale(zero=False),
  alt.Y('variety')
)

points = alt.Chart(source).mark_point(filled=True, color='black').encode(
  x=alt.X('mean(yield)'),
  y=alt.Y('variety'),
)

error_bars + points

Attribute syntax

import altair as alt
from vega_datasets import data

source = data.barley()

error_bars = alt.Chart(source).mark_errorbar(extent='ci').encode(
  x=alt.X('yield:Q', scale=alt.Scale(zero=False)),
  y=alt.Y('variety:N')
)

points = alt.Chart(source).mark_point(filled=True, color='black').encode(
  x=alt.X('yield:Q', aggregate='mean'),
  y=alt.Y('variety:N'),
)

error_bars + points