Hello, I perused the various threads on Relative Strength usage, and suspect I am in the right spot. But would like to clarify:

Is it possible to output a list of stocks calculated Relative Strength values for various look-back periods, eg RS 1month, 3month, 1 year etc? This would be a monthly process.

Is it possible to define this list of stocks by index membership? I read that Norgate has this in their data for US exchanges, but I have other non-US exchanges to work with as well. In the absence of index membership, I could probably just use market cap as a proxy.

The workflow would be: define the population of stocks per #2. Then calculate and output the RS values for each stock in that population. And rank them as a bonus, but can do that in Excel.

This is not for backtesting, it is an input to trading and the process is applied individually to various global exchanges on a monthly basis. Some retail online screener platforms offer the output I want, but I am so so so very tired of dealing with their bugs and problems in return for my money. I want to create and take ownership for my own solution once and for all.

Relative Strength is a RATIO between given symbol and index. It is does not use period. If you meant Relative Strength Index (RSI) instead, then you can have RSI of any period

Wikipedia is not always right. If you read it carefully you would see that they have two definitions that are different. The Wikipedia article you found, first talks about price ratio, then in second sentence it talks about ratio of ratios ("percentage change over some period" is a ratio by itself, called ROC - rate of change) . Classic Relative Strength is simply this ratio:

Close / Index_Close;

and it is not calculated over any period.

If you wish you can calculate ratio of ratios (ratio of ROCs), but this is not really Relative Strength, but "relative ROC"