This script implements the (mab) Volume Index (MVI) which is a volume momentum oscillator. The formula is similar to the formula of RSI but uses volume instead of price. The price is calculated as the average of open, high, low and close prices and is used to determine if the volume is counted as up-volume or down-volume.
I created MVI to replace OBV on my charts, because OBV is not as simple to read and find e.g. divergences. MVI is much easier to read because it is an oscillator with a minimum value of 0 and a maximum value of 100. It's easy to find divergences too. I like to display MVI over the volume bars. However, you can display it in a separate pain as well.