I couldn’t use your workflow because the data was not available, but I used the workflow prepared by Gabriel here Need help (very new to this field) with some more realistic price data. I also added a counter to the data to show the day number using the Counter Generation node.
I first changed the upward and downward movements to percentages in the expressions inside the Math Formula nodes. Then I calculated the moving average over a period of 14 days using the Moving Average node.
Then I lagged these gains by one row using the Lag Column node.
Finally I calculated the first, second, etc. RSIs using the Column Expressions node with the following code inside:
day = column("Counter")
RSI = null
if (day = 15)
RSI = 100 - (100/(1+(column("MA(Upward movement)")/14)/(column("MA(Downward Movement)")/14)))
if (day > 15)
RSI = 100 - (100/(1+(column("MA(Upward movement)(-1)")*13+column("Upward movement"))/(column("MA(Downward Movement)(-1)")*13+column("Downward Movement"))))