What is the difference between univariate and multivariate time series?

Question

I have the following time series data:

index              Time        value_1  value_2  value_3
 0        2016-04-01 06:00:10     1       5         2
 1        2016-04-01 06:00:20     2       9         8
 2        2016-04-01 06:00:30     3       5         1
 3        2016-04-01 06:00:40     4       4         4
 4        2016-04-01 06:00:50     3       4         5
 6        2016-04-01 06:01:00     4       3         2

Is this a univariate or a multivariate time series? What is the difference between univariate and multivariate time series?

Answer 1

Univariate time series: Only one variable is varying over time. For example, data collected from a sensor measuring the temperature of a room every second. Therefore, each second, you will only have a one-dimensional value, which is the temperature.

Multivariate time series: Multiple variables are varying over time. For example, a tri-axial accelerometer. There are three accelerations, one for each axis (x,y,z) and they vary simultaneously over time.

Considering the data you showed in the question, you are dealing with a multivariate time series, where value_1, value_2 andvalue_3 are three variables changing simultaneously over time.