Example of grouped bar chart with error bars

It took me a frustratingly long time to figure out how to do this, so I figured I would share an example if it was wanted for the gallery/tutorials/something else. In particular, dealing with the facet strictly after layering is a bit tricky.

Example 1: Grouped Bar Chart with Error Bars (note that color is not used, because then I cannot get the error bars to show up black)

import altair as alt
from vega_datasets import data

source = data.barley()

bars = alt.Chart().mark_bar().encode(
    x='year:O',
    y='mean(yield):Q',
    #color='year:N',
)

error_bars = bars.mark_rule().encode(
    x='year:O',
    y='ci0(yield):Q',
    y2='ci1(yield):Q'
)

alt.layer(bars, error_bars, data=source).facet(
    column='site:N'
)

Example 2: Grouped Plot with Error Bars (color can now be used easily)

import altair as alt
from vega_datasets import data

source = data.barley()

points = alt.Chart().mark_point(filled=True, size=50).encode(
    x='year:O',
    y=alt.Y('mean(yield):Q', title='Mean Yield'),
    color='year:N',
)

error_bars = bars.mark_rule().encode(
    x='year:O',
    y='ci0(yield):Q',
    y2='ci1(yield):Q'
)

alt.layer(points, error_bars, data=source).facet(
    column='site:N'
)

[bbrighttaer]

How can error bars be made to show on a grouped stacked bar chart using already calculated standard deviation values? I create the grouped stacked bar chart using Grant Langseth’s answer to this question. In my dataset, the standard deviation of each data point (appearing in a given stacked bar) is already determined and stored in another column. Thanks!

[bbrighttaer]

Hi @tigercosmos, I was not able to do this. I eventually had to change the chart type.