Quantmod Oscillators

Question

Utilizing the chartSeries function in the quantmod package, I want to modify the RSI oscillator. Given an xts object containing OHLC price data, here is the call that I am using:

chartSeries(plot_report[, 1:4],
        name        = substr(ticker, 1, nchar(ticker) - 4),
        theme       = chartTheme('white.mono', grid.col = NA),
        TA          = c(addRSI(n = 14, maType = "SMA")),
        type        = "line",
        bar.type    = 'ohlc',
        major.ticks = 'months',
        show.grid   = FALSE,
        log.scale   = TRUE)

Generating this chart:

I have four questions:

1. How can I change the default color of blue to something else? I have tried: c(addRSI(n = 14, maType = "SMA", col = "black")). However, I get the "unused argument" error.

2. Can I draw horizontal lines in the oscillator panel? Traditional RSI's have a horizontal red line at a y-axis value of 70 and a horizontal green line at a y-axis value of 30 to indicate overbought/oversold levels.

3. Is it possible to plot another calculation as an oscillator line below the chart? I have some proprietary oscillators that I want to visualize instead of the RSI or any of the indicators in the TTR package.

4. How can I get involved in improving the quantmod charting functionality; is this project being actively maintained?

Answer 1

1. You can't. You would need to add ... to the arguments for addRSI and modify the body of the function to use ... appropriately. A work-around is to calculate RSI manually, then call addTA as done in the answer to Change line colors of technical indicators made by R quantmod TTR?.
2. Use addLines:

getSymbols("SPY"); chartSeries(SPY, TA="addRSI();addLines(h=c(30,70), on=2)")

3. Use addTA with the object containing your proprietary data.
4. See quantmod's GitHub page. Yes, it's actively maintained. The last update was pushed to CRAN a couple months ago.