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I am working to calculate RSI (Relative Strength Index). I have data like this

**Date|Close|Change|Gain|Loss**

The formula for calculating this is

RSI = 100 - 100/(1+RS)
where RS = Average Gain / Average Loss

Source

So I want to calculate via some programming language either in JavaScript or C# but i don't know exactly how to convert that in programming language or what steps do I need.

If there is anything you want more to understand my problem i will try to explain.

Blu
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2 Answers2

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Simple way to translate the RSI formula:

public static double CalculateRsi(IEnumerable<double> closePrices)
{
    var prices = closePrices as double[] ?? closePrices.ToArray();

    double sumGain = 0;
    double sumLoss = 0;
    for (int i = 1; i < prices.Length; i++)
    {
        var difference = prices[i] - prices[i - 1];
        if (difference >= 0)
        {
            sumGain += difference;
        }
        else
        {
            sumLoss -= difference;
        }
    }

    if (sumGain == 0) return 0;
    if (Math.Abs(sumLoss) < Tolerance) return 100;

    var relativeStrength = sumGain / sumLoss;

    return 100.0 - (100.0 / (1 + relativeStrength));
}

There are plenty of projects implementing RSI in different ways. An incremental way can be found here

Donald Duck
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Ricardo stands with Ukraine
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    @AmirFo In this code was using `double Tolerance = 10e-20` just don't get an error in the division below. – Ricardo stands with Ukraine Apr 14 '20 at 12:39
  • For RelativeStrength we need to divide it by average of sum gain and average of sum loss.. so i feel in above code we need to change var relativeStrength = (sumGain/Period) / (sumLoss/Period).. reference from investopedia. RSI ​ =100−[ 100/( 1+ (Average loss/Average gain)) ] https://www.investopedia.com/terms/r/rsi.asp – Mehul Talajia Jun 07 '20 at 10:54
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I will write it in a pseudo code that you can easily write it in any languages. shortest way of coding it is:

v0 = 0 
v1 = 0 
v2 = 0 
v3 = 1/N                     
v4 = 0

if Step == 1: #initialisation
   v0 = (Price[t] - Price[t-N] ) / N
   v1 = mean( abs( diff(Price[(t-N):t] ) ) # average price change over previous N
else
   v2 = Price[t]  - Price[t-1] 
   v0 = vv[t-1] + v3 * ( v2 - v0[t-1] )
   v1 = v1[t-1] + v3 * ( abs( v2 ) - v1[t-1] )

if v1 != 0: 
   v4 = v0 / v1 
else
   v4 = 0

RSI = 50 * ( v4 + 1 )

This is probably the most efficient way of applying RSI in your simulation.

mm441
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