Convert discrete data from irregular duration event loop iterations to time series data using a Poisson window function

loop_to_timeseries.cc

/* Calculate the exponential moving average using the Poisson window function
 * combined with a time constant adjustment so even though the calculation is
 * only done once every loop, the smoothing curve acts as if it was time-series
 * data.
 *
 * The expanded equation for this is:
 *
 *                           /-ΔT \
 *                           |----|
 *                           \ τ  /
 *    s   =  s      + (1 - e       ) * (x  - s     )
 *     t      (t-1)                      t    (t-1)
 *
 * Where:
 *    ΔT - the difference in time since the last calculation in seconds
 *    τ  - the time constant for the calculation in seconds
 *    x  - new value to add to the exponential rolling avg
 */
static double inc_rolling_avg(double avg, double val, double diff, double con) {
  return avg + (1 - exp(-diff / con)) * (val - avg);
}