# Tracking number of value changes of boolean field in time series
**URL:** https://discuss.elastic.co/t/tracking-number-of-value-changes-of-boolean-field-in-time-series/290425
**Category:** Kibana
**Created:** [November 29, 2021, 11:05am UTC](https://discuss.elastic.co/t/tracking-number-of-value-changes-of-boolean-field-in-time-series/290425 "2021-11-29T11:05:06Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@DennisKlopfer](https://discuss.elastic.co/u/DennisKlopfer)
#### Post date: [November 29, 2021, 11:05am UTC](https://discuss.elastic.co/t/tracking-number-of-value-changes-of-boolean-field-in-time-series/290425/1 "2021-11-29T11:05:06Z")
My time series data contains a boolean field, which changes frequently. I want to count the number of changes of said field.
Optimally I would like to create a field containing this number while ingesting, but showing the current count on a Kibana Dashboard suffices.
I came up with the following approaches:
- Calculate a cummulative sum over the boolean field, filter by negative values and output the cardinality of the result.
- Use serial\_diff on the boolean field and sum over the result.
However I was not able to construct said queries or find dashboard functionality to represent this behaviour. Help is greatly appreceated.
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### Author:  [@Nathan\_Reese](https://discuss.elastic.co/u/Nathan_Reese)
#### Post date: [November 29, 2021, 6:31pm UTC](https://discuss.elastic.co/t/tracking-number-of-value-changes-of-boolean-field-in-time-series/290425/2 "2021-11-29T18:31:05Z")
Dashboards do no expose the ability to derive fields from multiple documents. To show this value in Kibana, you will need to store the value in the document.
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [December 27, 2021, 6:31pm UTC](https://discuss.elastic.co/t/tracking-number-of-value-changes-of-boolean-field-in-time-series/290425/3 "2021-12-27T18:31:23Z")
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