line chart showing data for different years, same month ?

Hi Paul

If this is what you're looking for:

...then this is how I made it, based upon your data:

load(
  local!monthNumbers: fn!enumerate(12)+1,
  local!monthNames: {
    "January",
    "February",
    "March:",
    "April",
    "May",
    "June",
    "July",
    "August",
    "September",
    "October",
    "November",
    "December"
  },
  
  local!data: {
    {year:2018,month:1,count:1},
    {year:2018,month:2,count: 54},
    {year:2018,month:3,count:123},
    {year:2019,month:1,count:347},
    {year:2019,month:4,count:503},
    {year:2019,month:5,count:52}
  },
  {
    a!lineChartField(
      categories: a!forEach(
        items: local!data,
        expression: fn!concat(
          fn!displayvalue(fv!item.month,local!monthNumbers, local!monthNames,""),
          " ",
          fv!item.year
        )
      ),
      series: a!chartSeries(
        label: "Month/Year",
        data: a!forEach(
          items: local!data,
          expression: fv!item.count
        )
      )
    )

  }
)

I might suggest that a line chart may not be the best way to represent this data as "number of widgets ordered per month" sounds quite discrete, and a line chart kind of communicates a more continuous set of changing data. But it;'s only my personal view.

load(
  local!data: {
    {
      year: 2018,
      month: 1,
      count: 1
    },
    {
      year: 2018,
      month: 2,
      count: 54
    },
    {
      year: 2018,
      month: 3,
      count: 123
    },
    {
      year: 2019,
      month: 1,
      count: 347
    },
    {
      year: 2019,
      month: 4,
      count: 503
    },
    {
      year: 2019,
      month: 5,
      count: 52
    }
  },
  local!months: {
    "Jan",
    "Feb",
    "Mar",
    "Apr",
    "May",
    "Jun",
    "Jul",
    "Aug",
    "Sep",
    "Oct",
    "Nov",
    "Dec"
  },
  local!years: union(
    local!data.year,
    local!data.year
  ),
  local!yearsData: a!forEach(
    items: local!years,
    expression: local!data[wherecontains(
      fv!item, tointeger(
        local!data.year
      )
    )]
  ),
  a!lineChartField(
    label: "Example:",
    categories: local!months,
    series: {
      a!forEach(
        items: local!yearsData,
        expression: a!chartSeries(
          label: local!years[fv!index],
          data: with(
            locaL!currentValue: fv!item,
            a!forEach(
              items: local!months,
              expression: if(
                isnull(
                  cast(
                    typeof(
                      1
                    ),
                    locaL!currentValue[wherecontains(
                      fv!index, tointeger(
                        local!currentValue.month
                      )
                    )].count
                  )
                ),
                0,
                cast(
                  typeof(
                    1
                  ),
                  locaL!currentValue[wherecontains(
                    fv!index, tointeger(
                      local!currentValue.month
                    )
                  )].count
                )
              )
            )
          )
        )
      )
    },
    xAxisTitle: "Month",
    yAxisTitle: "year",
    showLegend: true
  )
)

Nice!