The U.S. Employment Crash During the Great Recession

This example is a fully developed bar chart with negative values using the sample dataset of U.S. employment changes during the Great Recession.

Method syntax

import altair as alt
import pandas as pd
from vega_datasets import data

source = data.us_employment()
presidents = pd.DataFrame([
    {
        "start": "2006-01-01",
        "end": "2009-01-19",
        "president": "Bush"
    },
    {
        "start": "2009-01-20",
        "end": "2015-12-31",
        "president": "Obama"
    }
])
predicate = alt.datum.nonfarm_change > 0

bars = alt.Chart(
    source,
    title="The U.S. employment crash during the Great Recession"
).mark_bar().encode(
    alt.X("month:T").title(""),
    alt.Y("nonfarm_change:Q").title("Change in non-farm employment (in thousands)"),
    color=alt.when(predicate).then(alt.value("steelblue")).otherwise(alt.value("orange")),
)

rule = alt.Chart(presidents).mark_rule(
    color="black",
    strokeWidth=2
).encode(
    x='end:T'
).transform_filter(alt.datum.president == "Bush")

text = alt.Chart(presidents).mark_text(
    align='left',
    baseline='middle',
    dx=7,
    dy=-135,
    size=11
).encode(
    x='start:T',
    text='president',
    color=alt.value('#000000')
)

(bars + rule + text).properties(width=600)

Attribute syntax

import altair as alt
import pandas as pd
from vega_datasets import data

source = data.us_employment()
presidents = pd.DataFrame([
    {
        "start": "2006-01-01",
        "end": "2009-01-19",
        "president": "Bush"
    },
    {
        "start": "2009-01-20",
        "end": "2015-12-31",
        "president": "Obama"
    }
])
predicate = alt.datum.nonfarm_change > 0

bars = alt.Chart(
    source,
    title="The U.S. employment crash during the Great Recession"
).mark_bar().encode(
    x=alt.X("month:T", title=""),
    y=alt.Y("nonfarm_change:Q", title="Change in non-farm employment (in thousands)"),
    color=alt.when(predicate).then(alt.value("steelblue")).otherwise(alt.value("orange")),
)

rule = alt.Chart(presidents).mark_rule(
    color="black",
    strokeWidth=2
).encode(
    x='end:T'
).transform_filter(alt.datum.president == "Bush")

text = alt.Chart(presidents).mark_text(
    align='left',
    baseline='middle',
    dx=7,
    dy=-135,
    size=11
).encode(
    x='start:T',
    text='president',
    color=alt.value('#000000')
)

(bars + rule + text).properties(width=600)