Feature Request: Plot percent price change on the y-axis

Is your feature request related to a problem? Please describe.

When I want to compare two stocks, I'm interested in seeing the % changes in those two stocks over a period of time. Currently when I plot two stocks in mplfinance (using a secondary y-axis), I can't see the day-to-day percent changes, I only see the day-to-day price changes, which can be on different axes and thus inaccurate to compare directly.

For example, if I want to compare SPY and GOOG over a time period, I want to see the percent changes between the two (for easy comparison) rather than their stock prices which are almost an order of magnitude apart.

Describe the solution you'd like

A plot option that lets you plot the % change and lets you specify the start value that the percent changes should be compared against.

L’issue n’identifie aucun fichier ni test. Commencez par examiner l’API des options de tracé de mplfinance et le comportement actuel de l’axe Y secondaire, puis déterminez comment la comparaison des variations en pourcentage et une valeur de départ configurable doivent être spécifiées. Le travail est considéré comme terminé lorsque l’option produit des graphiques comparables des variations en pourcentage pour des symboles tels que SPY et GOOG, avec une couverture du nouveau comportement.