feat(sampler): add min-max sampler function

src/processor/dataSample.ts

@@ -61,6 +61,22 @@ const samplers: Dictionary<Sampler> = {
         // NaN will cause illegal axis extent.
         return isFinite(min) ? min : NaN;
     },
+    minmax: function (frame) {
+        let turningPointAbsoluteValue = -Infinity;
+        let turningPointOriginalValue = -Infinity;
+
+        for (let i = 0; i < frame.length; i++) {
+            const originalValue = frame[i];
+            const absoluteValue = Math.abs(originalValue);
+
+            if (absoluteValue > turningPointAbsoluteValue) {
+                turningPointAbsoluteValue = absoluteValue;
+                turningPointOriginalValue = originalValue;
+            }
+        }
+
+        return isFinite(turningPointOriginalValue) ? turningPointOriginalValue : NaN;
+    },
     // TODO
     // Median
     nearest: function (frame) {
@@ -116,4 +132,4 @@ export default function dataSample(seriesType: string): StageHandler {
             }
         }
     };
-}
+}

src/util/types.ts

@@ -1675,7 +1675,7 @@ export interface SeriesStackOptionMixin {
 type SamplingFunc = (frame: ArrayLike<number>) => number;
 
 export interface SeriesSamplingOptionMixin {
-    sampling?: 'none' | 'average' | 'min' | 'max' | 'sum' | 'lttb' | SamplingFunc
+    sampling?: 'none' | 'average' | 'min' | 'max' | 'minmax' | 'sum' | 'lttb' | SamplingFunc
 }
 
 export interface SeriesEncodeOptionMixin {