With time series data, the data always has two components; the timestamp and the value. While the timestamp is common for all data sources, the value type differs depending on the source.
The formats supported are as follows:
Numeric
Boolean
Period
String
Numeric
Numeric time series data is probably the most common format. In this case, the value component of the data is a number. The numeric value may also have an associated unit. An example of numeric time series data would be the temperature of a room:
timestamp | Room Temperature |
2019-01-01 00:00 | 20 °C |
2019-01-01 00:01 | 21 °C |
2019-01-01 00:02 | 19 °C |
With numeric time series data, is it possible to “fold” the data. For example, the average temperature of the above data is 20 °C and the maximum temperature is 21 °C.
Boolean
With Boolean time series data, the value component of the data is either TRUE or FALSE. An example of boolean time series data would be whether a valve is open or not:
timestamp | Valve Open |
2019-01-01 00:00 | TRUE |
2019-01-01 00:01 | TRUE |
2019-01-01 00:02 | FALSE |
It is not possible to fold boolean time series data using the numeric fold functions. For example, it is not possible to get the maximum value of the above data.
Often, boolean time series data is provided in a “Change of Value” format or “COV” for short. With COV data, values are only included when they are different to the previous value. The valve open example could be written in Boolean COV format as follows:
timestamp | Valve Open |
2019-01-01 00:00 | TRUE |
2019-01-01 00:02 | FALSE |
Notice that the second timestamp with a value of TRUE is omitted. This is because the value didn’t change from the previous timestamp so there’s no need to include it.
Period
With Period time series data, the value component of the data is a period of time. Technically it is a numeric series, but the value must be a number with a time unit. The value represents the period of time when some condition was true and the timestamp represents the start time. An example period grid would be the length of time a fan was running:
timestamp | Fan Run Time |
2019-01-01 00:30 | 1.5 hr |
2019-01-01 07:10 | 30 min |
2019-01-01 14:50 | 3 hr |
String
With String time series data, the value component is a string. An example of string time series data would be the operating mode of a machine
timestamp | Operating Mode |
2019-01-01 00:00 | “RUNNING” |
2019-01-01 06:25 | “SHUTTING DOWN” |
2019-01-01 06:40 | “OFF” |
As with boolean data, it is not possible to use numeric fold functions on string data.