Quantitative Analysis · Data Science · Machine Learning

# Relative Strength Index – RSI

## What is the RSI?

The relative strength index (RSI) is a financial indicator that measures the strength of a security’s price action. It is often used to identify overbought or oversold conditions in a market, as well as potential trend reversals.

The RSI is calculated by taking the average gain of the security over a certain number of periods and dividing it by the average loss over the same number of periods. This value is then converted into a scale from 0 to 100, with a value above 70 typically indicating an overbought condition and a value below 30 indicating an oversold condition.

To use the RSI, traders can plot the indicator on a chart and look for divergences between the indicator and the price action of the security. For example, if the price of a security is making new highs but the RSI is failing to do so, it may be a sign that the uptrend is losing momentum and a reversal could be imminent. Similarly, if the price of a security is making new lows but the RSI is not, it may be a sign that the downtrend is losing steam and a reversal could be on the horizon.

## Formula to calculate RSI

The formula to calculate the relative strength index (RSI) is as follows:

### RSI = 100 – (100 / (1 + RS))

where RS (relative strength) is calculated as:

### RS = Average gain over a certain number of periods / Average loss over the same number of periods

The number of periods used to calculate the RSI is typically 14, but it can be adjusted based on the trader’s preference and the specific security being analyzed.

To calculate the RSI, you will need to first determine the average gain and average loss over the specified number of periods. To do this, you will need to calculate the gain or loss for each period by subtracting the closing price of the period from the opening price. If the result is positive, it is considered a gain; if it is negative, it is considered a loss.

Once you have calculated the average gain and average loss for the specified number of periods, you can plug these values into the formula above to calculate the RSI. The resulting value will be a number between 0 and 100, with a value above 70 indicating an overbought condition and a value below 30 indicating an oversold condition.

It is important to note that the RSI should not be used in isolation and should be combined with other technical analysis tools and market analysis to form a complete trading strategy.

## There are several ways that the RSI can be used in an algorithmic trading strategy:

1. Overbought/oversold: One common way to use the RSI is to look for overbought and oversold conditions. An overbought condition occurs when the RSI is above 70, indicating that the security may be becoming overvalued and that a price reversal may be imminent. An oversold condition occurs when the RSI is below 30, indicating that the security may be undervalued and that a price reversal may be imminent.
2. Divergence: Another way to use the RSI is to look for divergences between the RSI and the security’s price. A bullish divergence occurs when the RSI is making higher lows while the security’s price is making lower lows, indicating that the security may be about to experience upward momentum. A bearish divergence occurs when the RSI is making lower highs while the security’s price is making higher highs, indicating that the security may be about to experience downward momentum.
3. Trend confirmation: The RSI can also be used to confirm trends in the security’s price. If the RSI is consistently above 50 and rising, it can be taken as a sign that the security is in an uptrend. Conversely, if the RSI is consistently below 50 and falling, it can be taken as a sign that the security is in a downtrend.

It’s important to note that the RSI should be used in conjunction with other technical analysis tools and fundamental analysis in order to provide a well-rounded view of a security’s market conditions.