fix augment

encoding.ts

@@ -57,11 +57,14 @@ export function polynomialFeatures(
 }
 
 /**
- * Adds missing rows at given interval, uses mean of previous and next value.
- * Example for one feature: [1, 2, 4, 5] -> [1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5]
+ * Add rows at given interval, use average to fill values.
+ * Usage:
+ * ```ts
+ * let df = augmentMeanForward("price", df, 100);
+ * ```
  * @param feature
  * @param df
- * @param bin
+ * @param interval
  */
 export function augmentMeanForward(
   feature: string,
@@ -69,27 +72,27 @@ export function augmentMeanForward(
   interval = 100,
 ) {
   let sorted = df.sort(feature);
-  let result = sorted.head(0);
-  let n: null | number = null;
-  for (let i = 0; i < sorted.height - 1; i++) {
-    let p1 = n ?? sorted.row(i).at(-1);
-    let p2 = sorted.row(i + 1).at(-1);
+  let featIdx = sorted.findIdxByName(feature);
+  let result = sorted.head(1);
+  for (let i = 0; i < sorted.height; i++) {
+    let p1 = sorted.row(i).at(featIdx);
+    let k = (i + 1) % sorted.height;
+    let p2 = sorted.row(k).at(featIdx);
     if (p2 - p1 > interval) {
-      let avg = (p1 + p2) / 2;
-      result = pl.concat([
-        result,
-        pl.concat([result.tail(2), sorted.slice({ offset: i + 1, length: 2 })])
-          .shift(-1)
-          .fillNull("mean")
-          .tail(1),
-      ]);
-      if (p2 - avg > interval) {
-        i--;
-        n = avg;
-        continue;
+      for (let j = 0; j < Math.round((p2 - p1) / interval) - 1; j++) {
+        result = pl.concat([
+          result,
+          pl.concat([
+            result.tail(1),
+            sorted.slice({ offset: k, length: 1 }),
+            sorted.head(1).shift(-1),
+          ])
+            .fillNull("mean")
+            .tail(1),
+        ]);
       }
+    } else {
       result = pl.concat([result, sorted.slice(1, i)]);
-      n = null;
     }
   }
   return result;