Calculating CUSUM

[Michelle Hart]

Question: How do you calculate the cusum using Seeq?

Answer: CUSUM is short for "cumulative sum." It is a formula used to determine the gradual change in a series of quantities over time. It can be easily calculated in Seeq with a few steps using point and click tools or with one Formula.

 

Steps using point and click tools: 

1. Use Periodic Condition to define the periods over which you want to do the cusum (hours, days, weeks, etc.).
2. Use Signal from Condition to find the average of the signal over the periodic condition.
3. Use Formula to do the signal minus the average.
4. Use Signal from Condition to calculate the sum of this new signal over the periodic condition. This will be your final answer, the cusum.

 

Formula:

You can copy this into Formula, name your desired signal $signal in the formula tool, and use your desired periodic condition if different than days:

$Periods = days() 

$average = $signal.aggregate(average(), $periods, durationkey()) 

$difference = $signal - $average 

$difference.aggregate(sum(), $periods, durationkey())