Indeed I have not yet heard of a strategy based on weekly bars. How would you backtest it with only a few hundred bars? But your code does not plot weekly candles anyway, it only defines a 7-days time frame. A candle is still 1 day.

For really plotting weekly candles, you had to either define an individual bar length with the bar() function, or plot them with rectangles. I guess that's probably not worth the hassle.