display month labels

altair-chart-in-progress.txt

date_chart1 = Chart(date_countsDF,  
      description='A linechart showing dates on x, and a count of turkey chemical residue tests on y'
     ).mark_line().encode(
    X('CollectDate:T', timeUnit='yearmonth'),
    Y('count:Q', aggregate='sum')
  )
date_chart1.configure_cell(height=270, width=800)
# date_chart1.configure_axis(ticks=20)

-----------
date_chart = Chart(date_countsDF, 
      description='A linechart showing dates on x, and a count of turkey chemical residue tests on y'
     ).mark_line().encode(
    x=X('CollectDate:T', 
        axis=Axis(labelAngle=320,labelBaseline="bottom", 
                  labelAlign="right", 
                  tickPadding=10,
                 ticks=40)),
    y='count:Q'
)
date_chart.configure_cell(height=270, width=800)
# date_chart.configure_axis(ticks=40)
date_chart.configure(timeFormat="%b %Y",)
# date_chart.encode?

vega-lite-charts.json

{
  "data": {"url": "data/seattle-weather.csv"},
  "mark": "bar",
  "encoding": {
    "x": {
      "timeUnit": "month",
      "field": "date",
      "type": "ordinal"
    },
    "column": {
        "field":"date",
        "timeUnit":"year",
        "type": "ordinal"
    },
    "y": {
      "aggregate": "mean",
      "field": "precipitation",
      "type": "quantitative"
    }
  }
}