domain gets calculated from

MapViewer.prototype._calculateMinMax = function (layer, metricFormula) {
  var minVal, maxVal
  layer.eachLayer(function (sublayer) {
    var metricVal = metricFormula(sublayer.feature.properties)
    if (!metricVal) return
    if (!(maxVal && minVal)) maxVal = metricVal, minVal = metricVal
    if (metricVal < minVal) {
      minVal = metricVal
    }
    if (metricVal > maxVal) {
      maxVal = metricVal
    }
  })
  return [minVal, maxVal]
}

This would return [undefined, undefined] incase the metric provided in the mapviewer options is Qualitative data.

Implications:

Even if domain is provided as array of unique categoricals and range as array of colors, the first color in range are already mapped to undefined value in domain. So, the domain mapping gets shifted by one place.

Possible Solutions: Create a domain calculator module in G1, that can take a accessor as parameter. Such that the input can be array of objects (collections), or an array itself. In mapviewer case, the input is an array of sublayer.feature.properties.

This g1.domain will be reused in g1.scales module.

Note for Tejesh: For discrete type scales (ordinal/band/point), if domain option is not provided and metric (Tejesh to make this as mandatory option) is provided, domain gets calculated internally irrespective of type of input data metric. If domain is provided but the provided domain does not span entire possible input values, discrete range values must be rotated after mapping provided domain values to discrete range.