How To Calculate Relative Strength Index (RSI) in PHP?

@samara 

To calculate the Relative Strength Index (RSI) in PHP, you can follow these steps:

1. First, gather the historical price data for the specified period (typically 14 days) for the asset or security you want to calculate the RSI for. You can fetch this data from a database or API.
2. Calculate the price change for each day by subtracting the current day's closing price from the previous day's closing price.
3. Separate the price changes into two lists - one for gains (positive changes) and one for losses (negative changes). Calculate the average gain and average loss for the specified period.
4. Calculate the Relative Strength (RS) by dividing the average gain by the average loss: RS = average gain / average loss.
5. Calculate the RSI using the formula: RSI = 100 - (100 / (1 + RS)).
6. Lastly, implement the RSI calculation in PHP code. Here is an example PHP function to calculate RSI:

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function calculateRSI($priceData, $period = 14) {
    $changes = [];
    
    for ($i = 1; $i < count($priceData); $i++) {
        $change = $priceData[$i] - $priceData[$i-1];
        $changes[] = $change;
    }
    
    $gains = $losses = [];
    
    foreach ($changes as $change) {
        if ($change > 0) {
            $gains[] = $change;
        } else {
            $losses[] = abs($change);
        }
    }
    
    $avgGain = array_sum($gains) / $period;
    $avgLoss = array_sum($losses) / $period;
    
    $RS = $avgGain / $avgLoss;
    
    $RSI = 100 - (100 / (1 + $RS));
    
    return $RSI;
}

// Example usage
$priceData = [50, 52, 55, 53, 56, 58, 57, 59, 60, 62, 61, 63, 65, 68];
$rsi = calculateRSI($priceData);
echo "RSI: " . $rsi;

This function takes an array of price data and calculates the RSI for the specified period (default is 14 days). You can adjust the period as needed for your analysis. The function returns the calculated RSI value.