// Licensed under the Apache License, Version 2.0
// © mihakralj
//@version=6
indicator("Rate of Change Ratio (ROCR)", "ROCR", overlay=false)

//@function Calculates ratio between current price and N periods ago
//@param source Source price series
//@param length Lookback period
//@returns Price ratio value
rocr(series float source, simple int length)=>
    if length<=0
        runtime.error("Length must be greater than 0")
    var int count = 0
    float ratio = na
    if not na(source[count]) and source[count] != 0
        ratio := source / source[count]
        count := math.min(count + 1, length)
    ratio

// ---------- Main loop ----------

// Inputs
i_source = input.source(close, "Source")
i_length = input.int(9, "Length", minval=1)

// Calculate ROCR
float rocr_val = rocr(i_source, i_length)

// Plot
plot(rocr_val, "ROCR", color=color.yellow, linewidth=2)