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SCFloatArrayRef RSI_S(SCFloatArrayRef In,
                SCFloatArrayRef RSIOut,
                SCFloatArrayRef UpSumsTemp,
                SCFloatArrayRef DownSumsTemp,
                SCFloatArrayRef SmoothedUpSumsTemp,
                SCFloatArrayRef SmoothedDownSumsTemp,
                int Index, unsigned int AveragingType, int Length)
{
  if (Length < 1 || Index < 1)
    return RSIOut;

  // calculate Up/Down sums
  float PreviousValue = In[Index - 1];
  float CurrentValue = In[Index];

  if (CurrentValue>PreviousValue)
  {
    // upward change
    UpSumsTemp[Index] = CurrentValue - PreviousValue;
    DownSumsTemp[Index] = 0;
  }
  else
  {
    UpSumsTemp[Index] = 0;
    DownSumsTemp[Index] = PreviousValue - CurrentValue;
  }

  // smooth the up/down sums
  MovingAverage_S(UpSumsTemp, SmoothedUpSumsTemp, AveragingType, Index, Length);
  MovingAverage_S(DownSumsTemp, SmoothedDownSumsTemp, AveragingType, Index, Length);

  // compute RSI
  if (SmoothedDownSumsTemp[Index] != 0.0f)
  {
    RSIOut[Index] = 100.0f - 100.0f / (1 + SmoothedUpSumsTemp[Index] / (SmoothedDownSumsTemp[Index]) );
  }
  else
  {
    RSIOut[Index] = RSIOut[Index - 1];
  }

  return RSIOut;
}