# What is a collection of time series called?

I am involved in an engineering project. We concern ourselves with a manufacturing process in which mechanical parts are processed. Every time a part is processed we get a set of time series data.

Let's say a part is produced in 5 seconds and we get temperature and torque with a rate of 1000 per second. So every Millisecond we write down the time (called timestamp) and the value and we do this for temperature and torque. Thus we get for each part two "lists" of time-value-pairs. Our system is not so exact so we cannot match up the time stamps exactly for both temperature and torque. Each of these lists is called a "time series" and for each time series we get about 5000 data entries (time-value-pairs). So for each processed part we have this data object which consists out of two time series. I am looking for a word for this data object. There is a mayor series of processed parts, where the parts are the elements of this series, but I am not concerned with that series.

With () being a pair and [] a list, we got

timeseries = [ (timestamp, value), ...(timestamp, value) ]
word = [ ('temperature', timeseries), ('torque', timeseries) ]
mayorsieries = [word, ..., word]


So in total we have a series of "word" that consists out of multiple time series. Thus I am looking for a word for "multiple time series that belong together". It is not "multivariate time series" because the timestamps are not aligned.

What does one call this data object in question?

• I would call such a data object a multivariate time series despite the timestamp for temperature and torque not being aligned. That's just an artifact of how these data are stored. You can view it as a missing data problem. As with any timeseries analysis, the first step will be to infer some type of continuous time trend before performing any inference or prediction. After that point, the alignment of timestamps for torque and temperature is no longer of concern. – AdamO Sep 12 '17 at 12:26
• I would call a time series a "crow" and therefore a related group of them that hang out together ought to be called a murder of crows. All facetiousness aside, could you tell us what your statistical question might be? – whuber Sep 12 '17 at 14:40
• @whuber: the question is regarding statistical nomenclature / terminology. – Make42 Sep 12 '17 at 15:03