I need to calculate some Bollinger Bands (BBs) for SwingTradeBot, which is built in Rails 4. Here’s a quick definition of Bollinger Bands: Bollinger Bands® are volatility bands placed above and below a moving average. Volatility is based on the standard deviation, which changes as volatility increases and decreases. So I needed to do some… Continue reading Calculating Standard Deviations in Ruby on Rails (and PostgreSQL)