Function columnHistogramQuery

packages/reltab/src/histogram.ts:49–102

(
  baseQuery: QueryExp,
  colId: string,
  colType: ColumnType,
  colStats: NumericSummaryStats
)

}

export function columnHistogramQuery(
  baseQuery: QueryExp,
  colId: string,
  colType: ColumnType,
  colStats: NumericSummaryStats
): NumericColumnHistogramQuery | null {
  const minVal = colStats.min;
  const maxVal = colStats.max;

  if (minVal == null || maxVal == null || minVal === maxVal) {
    return null;
  }
  const binCount = binsForColumn(colStats);

  const [niceMinVal, niceMaxVal] = nice(minVal, maxVal, binCount);

  const binWidth = (niceMaxVal - niceMinVal) / binCount;

  // add a column with bin number:
  const binQuery = baseQuery
    .extend("column", constVal(colId))
    .extend(
      "bin",
      cast(
        floor(
          divide(
            minus(
              cast(col(colId), doubleType),
              cast(constVal(niceMinVal), doubleType)
            ),
            cast(constVal(binWidth), doubleType)
          )
        ),
        intType
      )
    );

  const histoQuery = binQuery
    .extend("binCount", constVal(1))
    .project(["column", "bin", "binCount"])
    .groupBy(["column", "bin"], [["count", "binCount"]]);

  const ret = {
    colId,
    histoQuery,
    minVal,
    maxVal,
    niceMinVal,
    niceMaxVal,
    binCount,
    binWidth,
  };
  return ret;
}

// histogram data for rendering a single column histogram
export interface NumericColumnHistogramData {