Hi everyone,

I'm Med Student and new using STATA. Currently, For a systolic blood pressure visit to visit (long term) variability analysis study, I have a database with the repeated measurements of blood pressure in a considerably large sample. Each individual has a record of approximately 7 visits that were performed at different times. I am currently at a "bottleneck" due to not being able to calculate Average Real Variability (ARV). The ARV is defined as the average of the absolute differences between all consecutive BP measurements. The ARV formula is as follows:

where k ranges from 1 to n-1, and n is the number of blood pressure readings.

I do not know how I could run this formula considering the number of subjects and the number of repeated blood pressure measurements, I would greatly appreciate your help.