This indicator was originally noted in the tradingview help forums. Noted from "Google's Finance Site," but they use a modified (using EMA instead of traditional SMA) slow stochastic with the %J equation (%J =3 * D – 2 * K ). I can't find any references to the origins of the %J equation, but it is noted in several other online sites. getsatisfaction.com/tradingview/topics/pine_script_for_kdj_indicator
So, I've taken the indicator and made some options, upgrades and published it for free!. The basic foundation of the code is still the %J equation. I've included an option to use either the EMA (default) and the SMA (more traditional slow stochastic). You can also adjust the lookback period, %D smoothing, and I've included the option to smooth the %J. This last option slows the indicator down a little, but really cuts out the choppiness of the %J crossings.