diff --git a/src/shared/heikinashi.ts b/src/shared/heikinashi.ts
index 4c60974a..c0966f62 100644
--- a/src/shared/heikinashi.ts
+++ b/src/shared/heikinashi.ts
@@ -4,23 +4,15 @@ export default function heikinAshiDataset(columns: string[], data: Array<number[
   const highIdx = columns.indexOf('high');
   const lowIdx = columns.indexOf('low');
 
-  return data.map((original, idx, candles) => {
+  let prevCandle: number[];
+  return data.map((original, idx) => {
     // Prevent mutation of original data
     const candle = original.slice();
-
-    if (idx === 0) {
-      const close = (candle[openIdx] + candle[highIdx] + candle[lowIdx] + candle[closeIdx]) / 4;
-      const open = (candle[openIdx] + candle[closeIdx]) / 2;
-
-      candle[openIdx] = open;
-      candle[closeIdx] = close;
-
-      return candle;
-    }
-
-    const prevCandle = candles[idx - 1];
+    const open =
+      idx === 0
+        ? (candle[openIdx] + candle[closeIdx]) / 2
+        : (prevCandle[openIdx] + prevCandle[closeIdx]) / 2;
     const close = (candle[openIdx] + candle[highIdx] + candle[lowIdx] + candle[closeIdx]) / 4;
-    const open = (prevCandle[openIdx] + prevCandle[closeIdx]) / 2;
     const high = Math.max(candle[highIdx], candle[openIdx], candle[closeIdx]);
     const low = Math.min(candle[lowIdx], candle[openIdx], candle[closeIdx]);
 
@@ -29,6 +21,8 @@ export default function heikinAshiDataset(columns: string[], data: Array<number[
     candle[highIdx] = high;
     candle[lowIdx] = low;
 
+    prevCandle = candle.slice();
+
     return candle;
   });
 }